Đề số 1

ĐỀ THI THỬ THPTQG 2017 TRẮC NGHIỆM MÔN TIẾNG ANH ĐỀ THI THỬ SỐ Mark the letter A, B, C, or D on your answer sheet to indicate the word whose underlined part differs from the other three in pronunciation in each of the following questions Question 1: A justice B campus C culture D brush Question 2: A pressure B assure C assist D possession Mark the letter A, B, C, or D on your answer sheet to indicate the word that differs from the other three in the position of primary stress in each of the following questions Question 3: A reduction B popular C romantic D financial Question 4: A concentrate B eventual C character D transcript Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in the each of following questions Question 5: Looking (A) from afar, the village resembles (B) a small green (C) spot dotted with (D) tiny fireballs Question 6: When (A) the chemicals inside (B) a cell no longer (C) produce ions, the cell stops to function (D) Question 7: I can’t stand make (A) noise in class Would (B) you please something (C) more useful (D)? Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions Question 8: The Lake District, _ was made a national park in 1951, attracts a large number of tourists every year A that B where C what D which Question 9: The _ north we go, the less likely we are to meet high temperatures A far B further C farther D farthest Question 10: _ the weather forecast, it will rain heavily later this morning A On account of B According to C Due to D Because of Question 11: I _ the bell three times when he answered the door A had rung B rang C would ring D was ringing Question 12: The vegetation in the jungle made it difficult to spot snakes and lizards A heavy B elaborate C thick D lush Question 13: “Do you like the weather here?” - “I wish it _.” A doesn’t rain B didn’t rain C won’t rain Question 14: She should have been here but she’s _ flu Đề số D hadn’t rained A gone thought with B come in for C gone down with D come against Question 15: No sooner _ my car than the alarm went off A the thief had touched B had the thief touched C touched the thief D the thief touched Question 16: The doctor told him to keep _ sweets and chocolate to lose weight A off B up C at D back Question 17: You _ that book last year - it only came out two weeks ago A can’t have read B mustn’t have read C shouldn’t have red D needn’t have read Question 18: Are you having a _ exam before you sit the actual exam in July? A fake B false C mock D counterfeit Question 19: There should be an international law against _ A reforestation B forestry C deforestation D afforestation Mark the letter A, B, C, or D on your answer sheet to indicate the most suitable response to complete each of the following exchanges Question 20: Bob: “Our team has just won the last football match.” Michael: “ _!” A Good idea Thanks for the news B Yes I guess it’s very good C Well, that’s very surprising D Yes, it’s our pleasure Question 21: “ _” - “Oh, it’s great!” A How is the English competition like? B Would you like the English competition? C What you like about the English competition? D What you think of the English competition? Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) CLOSEST in meaning to the underlined word(s) in each of the following questions Question 22: The introduction of credit cards radically modified North Americans’ spending habits A reduced B altered C resolved D devoted Question 23: The bread has become stale and I cannot swallow it A gone away B gone down C gone up D gone off Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) OPPOSITE in meaning to the underlined word(s) in each of the following questions Question 24: She came for Christmas laden with gifts for everyone A later B provided Đề số C unloaded D lifted Question 25: Population growth rates vary among regions and even among countries within the same region A restrain B stay unchanged C remain unstable D fluctuate Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions Question 26: While I strongly disapproved of your behavior, I will help you this time A Despite of my strong disapproval of your behavior, I will help you this time B Although I strongly disapproved of your behavior, but I will help you this time C Because of your behavior, I will help you this time D Despite my strong disapproval of your behavior, I will help you this time Question 27: Nothing but the whole story would satisfy Jane A Jane wouldn’t be satisfied with anything B Jane insisted on being told the complete story C On the whole, Jane was satisfied with the story D Jane wanted to know just the end of the story Question 28: Mary might have phoned while we were out A Possibly Mary phoned while we were out B Unfortunately we were out while Mary phoned C We were sure Mary had phoned while we were out D Mary ought to have phoned while we were out Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions Question 29: The student next to me kept chewing gum That bothered me a lot A The student next to me kept chewing gum, that bothered me a lot B The student next to me kept chewing gum, which bothered me a lot C The student next to me kept chewing gum bothering me a lot D The student next to me kept chewing gum bothered me a lot Question 30: The police issued a warning on the radio A dangerous man had escaped from hospital A A dangerous man had escaped from hospital, so the police issued a warning on the radio B The police issued a warning on the radio about a dangerous man had escaped from hospital C The police issued a warning on the radio, namely, a dangerous man had escaped from hospital D A dangerous man had escaped from hospital where the police issued a warning on the radio Đề số Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 31 to 35 Early writing and Alphabets When people first began to write, they did not use an alphabet Instead, they drew small pictures to (31) _ the objects they were writing about This was very slow because there was a different picture for any word The Ancient Egyptians had a system of picture writing that was described hieroglyphics The meaning of this writing was forgotten for a very long time but in 1799 some scientists (32) _ a stone near Alexandria, in Egypt The stone had been there for (33) _ a thousand years It had both Greek and hieroglyphics on it and researchers were finally able to understand what the hieroglyphics meant An alphabet is quite different from picture writing It (34) _ of letters or symbols that represent a sound and each sound is just part of one word The Phoenicians, who lived about 3,000 years ago, developed the modern alphabets It was later improved by the Roman’s and this alphabet is now used (35) _ throughout the world Question 31: A notice B show C appear D mark Question 32: A discovered B realized C delivered D invented Question 33: A quite B more C over D already Question 34: A consistsof B includes C contains D involves Question 35: A broadly B widely C deeply D hugely Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 36 to 42 Homing pigeons are placed in a training program from about the time they are twenty-eight days of age They are taught to enter the loft through a trap and to exercise above and around the loft, and gradually they are taken away for short distances in wicker baskets and released They are then expected to find their way home in the shortest possible time In their training flights or in actual races, the birds are taken to prearranged distant points and released to find their way back to their own lofts Once the birds are liberated, their owners, who are standing by at the home lofts, anxiously watch the sky for the return of their entries Since time is of the essence, the speed with which the birds can be induced to enter the loft trap may make the difference between gaining a win or a second place The head of a homing pigeon is comparatively small, but its brain is one quarter larger than that of the ordinary pigeon The homing pigeon is very intelligent and will persevere to the point of stubbornness some have been known to fly a hundred miles off course to avoid a storm Đề số Some homing pigeon experts claim that this bird is gifted with a form of built-in radar that helps it find its own loft after hours of flight, for hidden under the head feathers are two very sensitive ears, while the sharp, prominent eyes can see great distances in daytime Why homing pigeons fly home? They are not unique in this inherent skill: it is found in most migratory birds, in bees, ants, toads, and even turtles, which have been known to travel hundreds of miles to return to their homes But in the animal world, the homing pigeon alone can be trusted with its freedom and trained to carry out the missions that people demand Question 36: What is the purpose of the passage? A To convince the reader to buy a homing pigeon B To inform the reader about homing pigeons and their training C To protect homing pigeons against the threat of extinction D To encourage the owners of homing pigeons to set the birds free Question 37: According to the passage, what happens to homing pigeons when they are about a month old? A They are kept in a trap B They enter their first race C They begin a training program D They get their wings clipped and marked Question 38: In line 7, when the author states that the owners "anxiously watch the sky" there is the implication that the owners A want their pigeon to win the race B are sending radar signals to their pigeons C not know whether the race began on time D not trust the rules set down by the judges Question 39: According to the passage, what is the difference between a homing pigeon and an ordinary one? A The span of the wings B The shape of the eyes C The texture of the feathers D The size of the brain Question 40: The author mentions all of the following at tributes that enable a homing pigeon to return home EXCEPT A instinct B air sacs C sensitive ears D good eyes Question 41: In line 12, the pronoun "it" refers to which of the following? A Radar B Bird C Loft D Form Question 42: Why does the author mention bees, ants, toads, and turtles in the last paragraph? A To describe some unusual kinds of pets B To measure distances traveled by various animals C To compare their home-finding abilities with those of homing pigeons D To interest the reader in learning about other animals Đề số Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 43 to 50 If the salinity of ocean waters is analyzed, it is found to vary only slightly from place to place Nevertheless, some of these small changes are important There are three basic processes that cause a change in oceanic salinity One of these is the subtraction of water from the ocean by means of evaporationconversion of liquid water to water vapor In this manner, the salinity is increased, since the salts stay behind If this is carried to the extreme, of course, white crystals of salt would be left behind: this, by the way, is how much of the table salt we use is actually obtained The opposite of evaporation is precipitation such as rain, by which water is added to the ocean Here the ocean is being diluted so that the salinity is decreased This may occur in areas of high rainfall or in coastal regions where rivers flow into the ocean Thus salinity may be increased by the subtraction of water by evaporation, or decreased by the addition of fresh water by precipitation or runoff Normally in tropical regions where the Sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation Similarly, in coastal regions where rivers dilute the sea salinity is somewhat lower than in other oceanic areas A third process by which salinity may be altered is associated with the formation and melting of sea ice When seawater is frozen, the dissolved materials are left behind In this manner, seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared Of course, when this ice melts, it will tend to decrease the salinity of the surrounding water In the Weddell Sea, off Antarctica, the densest water in the oceans is formed as a result of this freezing process, which increases the salinity of cold water This heavy water sinks and is found in the deeper portions of the oceans of the world Question 43: What does the passage mainly discuss? A The bodies of water of the world B The elements of salt C The many forms of ocean life D The salinity of ocean water Question 44: According to the passage, the ocean generally has more salt in A coastal areas B tropical areas C rainy areas D turbulent areas Question 45: All of the following are processes that decrease salinity EXCEPT A evaporation B precipitation C runoff D melting Question 46: Which of the following statements about the salinity of a body of water can best be inferred from the passage? A The temperature of the water is the most important factor B How quickly the water moves is directly related to the amount of alt C Ocean salinity has little effect on sea life D Various factors combine to cause variations in the salt content of water Question 47: The word "it" in line 16 refers to which of the following? Đề số A Sea ice B Salinity C Seawater D Manner Question 48: Why does the author mention the Weddell Sea? A To show that this body of water has salinity variations B To compare Antarctic waters with Arctic waters C To give an example of cold-water salinity D To point out the location of deep waters Question 49: Which of the following is NOT a result of the formation of ocean ice? A The salt remains in the water B The surrounding water sinks C Water salinity decreases D The water becomes denser Question 50: What can be inferred about the water near the bottom of oceans? A It is relatively warm B Its salinity is relatively high C It does not move D It is formed by melting sea ice Đề số Đáp án 1-B 2-C 3-B 4-B 5-A 6-D 7-A 8-D 9-C 10-B 11-A 12-C 13-B 14-C 15-B 16-A 17-A 18-C 19-C 20-C 21-D 22-B 23-D 24-C 25-B 26-D 27-B 28-A 29-B 30-A 31-B 32-A 33-C 34-A 35-B 36-B 37-C 38-A 39-D 40-B 41-B 42-C 43-D 44-B 45-A 46-D 47-C 48-C 49-C 50-B LỜI GIẢI CHI TIẾT Question 1: Đáp án B Từ “campus” có phần gạch chân phát âm /ə/ Các từ lại có phần gạch chân phát âm /ʌ/ Question 2: Đáp án C Từ “assist” có phần gạch chân phát âm /s/ Các từ lại có phần gạch chân phát âm /ʃ/ Question 3: Đáp án B Từ “popular” có trọng âm rơi vào âm tiết thứ Các từ lại có trọng âm rơi vào âm tiết thứ hai Question 4: Đáp án B Từ “eventual” có trọng âm rơi vào âm tiết thứ hai Các từ lại có trọng âm rơi vào âm tiết thứ Question 5: Đáp án A Khi mệnh đề chủ ngữ, ta rút gọn mệnh đề trước V-ing (HTPT) mang nghĩa chủ động PII (QKPT) mang nghĩa bị động Câu mang nghĩa bị động →A đáp án sai Chữa lỗi: Looking →Looked Dịch: Khi nhìn từ xa, ngơi làng giống cầu lửa với đốm nhỏ màu xanh nằm rải rác Question 6: Đáp án D Stop + V-ing: dừng làm việc Stop + to V: dừng (làm gì) để làm Chữa lỗi: to function → functioning Dịch: Khi thành phần hóa học bên tế bào không sản xuất ion, tế bào ngừng hoạt động Question 7: Đáp án A Can’t stand + V-ing: chịu việc Chữa lỗi: make → making Đề số Dịch: Tôi chịu việc gây ồn lớp Làm ơn làm thứ có ích khơng? Question 8: Đáp án D Thay cho N vật làm chủ ngữ → dùng “which” Dịch: Lake District, lập thành vườn quốc gia vào năm 1951, thu hút số lượng lớn khách du lịch năm Question 9: Đáp án C Dạng so sánh kép → loại A, D Farther: dùng với đặc tính tự nhiên, dùng để miêu tả cự ly địa lý (có thể quan sát, cảm nhận tự đánh giá) Further: dùng với nghĩa trừu tượng, dùng để mức độ không gian, thời gian,… Dịch: Chúng ta xa phía Nam, có khả gặp phải nhiệt độ cao Question 10: Đáp án B On account of: trường hợp According to sth: theo Due to + N: (thường dùng với nghĩa tiêu cực) Because of + N: Dịch: Theo dự báo thời tiết, trời mưa lớn sau sáng Question 11: Đáp án A Diễn tả hành động xảy trước hành động khác q khứ → dùng QKHT Dịch: Tơi nhấn chuông lần anh mở cửa Question 12: Đáp án C Heavy (adj): nặng Elaborate (adj): kỹ lưỡng Thick (adj): dày, rậm rạp Lush (adj): tươi tốt Dịch: Thảm thực vật rậm rạp rừng làm cho khó phát rắn thằn lằn Question 13: Đáp án B Diễn tả mong muốn khơng HT với “wish” → dùng QKĐ (“tobe” chia “were” với chủ ngữ) Dịch: “Bạn có thích thời tiết khơng?” – “Tơi ước trời khơng mưa.” Question 14: Đáp án C Come in for: hứng chịu (lời phê bình, trích) Go down with: bị (bệnh) Dịch: Cô đáng cô bị cảm Question 15: Đáp án B Cấu trúc: No sooner + had + S + PII … than + S + V (past) …: vừa mới… thì… Dịch: Tên trộm vừa chạm vào xe chng cảnh báo reo lên Đề số Question 16: Đáp án A Keep off: tránh xa Keep up: giữ gìn Keep at: kiên trì (làm việc) Dịch: Bác sĩ bảo anh tránh xa đồ sô-cô-la để giảm cân Question 17: Đáp án A Diễn tả dự đoán hành động, việc xảy khứ → dùng “can’t have + PII” Dịch: Bạn đọc sách năm ngối – xuất tuần trước Question 18: Đáp án C Mock test/ exam: kỳ thi thử Fake (n): vật làm giả, đồ giả mạo False (adj): sai, nhầm/ không thật, giả Counterfeit (adj): giả, giả mạo (counterfeit money: tiền giả) Dịch: Bạn có kỳ thi thử trước bạn thi kỳ thi thức vào tháng Bảy không? Question 19: Đáp án C Reforestation (n): tái trồng rừng Forestry (n): lâm nghiệp Deforestation (n): nạn phá rừng Afforestation (n): rừng Dịch: Nên có luật quốc tế chống nạn phá rừng Question 20: Đáp án C Bob: “Đội thắng trận đá bóng chung kết rồi.” Michael: “Ồ, thật đáng ngạc nhiên!” Question 21: Đáp án D “Bạn nghĩ kỳ thi tiếng Anh?” – “Oh, thật tuyệt!” Question 22: Đáp án B Modify (v) ~ alter (v): thay đổi Reduce (v): giảm Resolve (v): định Devote (v): cống hiến Dịch: Sự đời thẻ tín dụng làm thay đổi hồn tồn thói quen chi tiêu người Bắc Mỹ Question 23: Đáp án D Stale (adj) ~ go off: có mùi hơi, hỏng Dịch: Cái bánh mỳ bị hỏng khơng thể nuốt Question 24: Đáp án C Lade (v): mang theo, chất đầy >< unload (v): dỡ bỏ 10 Đề số Later (adv): sau Provide (v): cung cấp Lift (v): nhấc Dịch: Cô đến vào Giáng Sinh mang theo quà cho người Question 25: Đáp án B Vary (v): khác nhau, thay đổi >< Stay unchanged: giữ nguyên, không thay đổi Restrain (v): giữ lại, ngăn lại Remain unstable: không ổn định Fluctuate (v): biến động, thay đổi Dịch: Tỷ lệ gia tăng dân số khác vùng miền chí đất nước vùng Question 26: Đáp án D Đề: Trong tơi hồn tồn khơng tán thành thái độ bạn, giúp bạn thời gian Đáp án C không hợp nghĩa → loại C Although + SVO, SVO…: …, nhưng… → loại B (thừa “but”) Despite + N/ V-ing, SVO…: Mặc dù…, nhưng… → chọn D Dịch: Mặc phù hồn tồn khơng tán thành thái độ bạn, giúp bạn thời gian Question 27: Đáp án B Đề: Khơng có ngồi tồn câu chuyện làm thỏa mãn Jane Các đáp án A, C, D không nghĩa Cấu trúc: insist on + V-ing: khăng khăng làm Dịch: Jane khăng khăng đòi kể cho nghe tồn câu chuyện Question 28: Đáp án A Đề: Mary gọi điện đến Cấu trúc: might + have + PII: làm (diễn tả dự đốn xảy QK) → đáp án B, C, D không hợp nghĩa Dịch: Có thể Mary gọi điện đến Question 29: Đáp án B Đề: Cậu học sinh bên cạnh nhai kẹo cao su Điều làm phiền tơi nhiều Nối câu mệnh đề quan hệ, ta dùng “which” để thay cho mệnh đề trước dấu phẩy Dịch: Cậu học sinh bên cạnh nhai kẹo cao su, mà điều làm phiền tơi nhiều Question 30: Đáp án A Đề: Cảnh sát đưa cảnh báo đài phát Một người đàn ơng nguy hiểm trốn khỏi bệnh viện Các đáp án B, C, D không nghĩa → chọn A 11 Đề số Dịch: Một người đàn ơng nguy hiểm trốn khỏi bệnh viện, cảnh sát đưa lời cảnh báo đài phát Question 31: Đáp án B Notice (v): ý Show (v): cho biết, Appear (v): có vẻ, giống Mark (v): đánh dấu Dịch: “… Thay vào đó, họ vẽ vẽ nhỏ để vật thể mà họ viết…” Question 32: Đáp án A Discover (v): khám phá, phát Realize (v): nhận Deliver (v): phân phát Invent (v): phát minh, sáng chế Dịch: “… Ý nghĩa viết bị lãng quên suốt thời gian dài vào năm 1799 số nhà khoa học phát tảng đá gần Alexandria, Ai Cập…” Question 33: Đáp án C Over + a period of time: … Dịch: “… Tảng đá khoảng nghìn năm…” Question 34: Đáp án A Consist of: bao gồm Dịch: “… Nó bao gồm nhiều ký tự biểu tượng mà thể âm âm phần từ…” Question 35: Đáp án B Broadly (adv): chung, đại khái, đại thể Widely (adv): cách rộng rãi Deeply (adv): cách sâu sắc Hugely (adv): đỗi, Dịch: “… bảng chữ sử dụng cách rộng rãi khắp giới.” Question 36: Đáp án B Nội dung xoay quanh đặc điểm chim bồ câu dẫn đường trình huấn luyện chúng → chọn B Mục tiêu viết để thông tin cho người đọc chim bồ câu dẫn đường huấn luyện chúng Question 37: Đáp án C Thông tin “Homing pigeons are placed in a training program from about the time they are twentyeight days of age” → Khi chim bồ câu dẫn đường khoảng tháng tuổi, chúng bắt đầu trình huấn luyện 12 Đề số Question 38: Đáp án A Thông tin “In their training flights or in actual races, the birds are taken to prearranged distant points and released to find their way back to their own lofts Once the birds are liberated, their owners, who are standing by at the home lofts, anxiously watch the sky for the return of their entries” → tác giả chủ nhân chim muốn chúng thắng đua nhìn cách lo lắng lên bầu trời Question 39: Đáp án D Thông tin “The head of a homing pigeon is comparatively small, but its brain is one quarter larger than that of the ordinary pigeon” → khác chim bồ câu dẫn đường chim bồ câu thông thường kích thước não Question 40: Đáp án B Thông tin “…for hidden under the head feathers are two very sensitive ears, while the sharp, prominent eyes can see great distances in daytime” “They are not unique in this inherent skill” → Một đôi tai nhạy cảm, đôi mắt tốt tính vốn có giúp chim bồ câu dẫn đường trở nhà → Đáp án B không đề cập → chọn B Question 41: Đáp án B Câu “Some homing pigeon experts claim that this bird is gifted with a form of built-in radar that helps it find its own loft after hours of flight” → Đại từ “it” câu đề cập đến danh từ “bird” Question 42: Đáp án C Thông tin “Why homing pigeons fly home? They are not unique … the missions that people demand.” → tác giả đề cập đến loài động vật khác nhằm so sánh khả tìm đường nhà chúng với khả tìm đường nhà chim bồ câu dẫn đường Question 43: Đáp án D Dựa vào câu mở đầu “If the salinity of ocean waters is analyzed, it is found to vary only slightly from place to place” thông tin đề cập đến toàn đoạn văn → đoạn văn chủ yếu thảo luận độ mặn nước biển Question 44: Đáp án B Thông tin “Normally in tropical regions where the Sun is very strong, the ocean salinity is somewhat higher than it is in other parts of the world where there is not as much evaporation” → biển thơng thường có nhiều muối khu vực nhiệt đới Question 45: Đáp án A Thông tin “… salinity may be increased by the subtraction of water by evaporation, or decreased by the addition of fresh water by precipitation or runoff…” “when this ice melts, it will tend to decrease the salinity of the surrounding water” 13 Đề số → Các đáp án B, C, D đề cập đến trình làm giảm độ mặn Question 46: Đáp án D Dựa vào thông tin đề cập đoạn văn → suy có nhiều nhân tố kết hợp lại để gây thay đổi lượng muối nước biển Question 47: Đáp án C Thông tin “… seawater directly beneath freshly formed sea ice has a higher salinity than it did before the ice appeared” → từ “it” dạng thay danh từ “seawater” Question 48: Đáp án C Dựa vào thông tin đề cập đoạn cuối → tác giả đề cập đến biển Weddell ví dụ độ mặn nước lạnh Question 49: Đáp án C Thông tin đoạn cuối “…the densest water in the oceans is formed as a result of this freezing process, which increases the salinity of cold water This heavy water sinks…” → hình thành băng biển KHÔNG làm giảm độ mặn nước biển Question 50: Đáp án B Đoạn cuối “In the Weddell Sea, off Antarctica, the densest water in the oceans is formed as a result of this freezing process, which increases the salinity of cold water This heavy water sinks and is found in the deeper portions of the oceans of the world” → suy độ mặn nước gần đáy biển tương đối cao 14 Đề số ... by melting sea ice Đề số Đáp án 1- B 2-C 3-B 4-B 5-A 6-D 7-A 8-D 9-C 10 -B 11 -A 12 -C 13 -B 14 -C 15 -B 16 -A 17 -A 18 -C 19 -C 20-C 21- D 22-B 23-D 24-C 25-B 26-D 27-B 28-A 29-B 30-A 31- B 32-A 33-C 34-A... viện Các đáp án B, C, D không nghĩa → chọn A 11 Đề số Dịch: Một người đàn ơng nguy hiểm trốn khỏi bệnh viện, cảnh sát đưa lời cảnh báo đài phát Question 31: Đáp án B Notice (v): ý Show (v): cho biết,... decrease the salinity of the surrounding water” 13 Đề số → Các đáp án B, C, D đề cập đến trình làm giảm độ mặn Question 46: Đáp án D Dựa vào thông tin đề cập đoạn văn → suy có nhiều nhân tố kết hợp