PASSAGE 22 Although only a small percentage of the electromagnetic radiation that is emitted by the Sun is ultraviolet (UV) radiation, the amount that is emitted would be enough to cause severe damage to most forms of life on Earth were it all to reach the surface of the Earth Fortunately, all of the Sun’s ultraviolet radiation does not reach the Earth because of a layer of oxygen, called the ozone layer encircling the Earth in the stratosphere at an altitude of about 15 miles above the Earth The ozone layer absorbs much of the Sun’s ultraviolet radiation and prevents it from reaching the Earth Ozone is a form of oxygen in which each molecule consists of three atoms (O3) instead of the two atoms (O2) usually found in an oxygen molecule Ozone forms in the stratosphere in a process that is initiated by ultraviolet radiation from the Sun UV radiation from the Sun splits oxygen molecules with two atoms into free oxygen atoms, and each of these unattached oxygen atoms then joins up with an oxygen molecule to form ozone UV radiation is also capable of splitting up ozone molecules; thus, ozone is constantly forming, splitting, and reforming in the stratosphere When UV radiation is absorbed during the process of ozone formation and reformation, it is unable to reach Earth and cause damage there Recently, however, the ozone layer over parts of the Earth has been diminishing Chief among the culprits in the case of the disappearing ozone, those that are really responsible, are the chlorofluorocarbons (CFCs) CFCs meander up from Earth into the stratosphere, where they break down and release chlorine The released chlorine reacts with ozone in the stratosphere to form chlorine monoxide (CIO) and oxygen (O2) The chlorine then becomes free to go through the cycle over and over again One chlorine atom can, in fact, destroy hundreds of thousands of ozone molecules in this repetitious cycle, and the effects of this destructive process are now becoming evident Question According to the passage, ultraviolet radiation from the Sun A is causing severe damage to the Earth's ozone layer B is only a fraction of the Sun's electromagnetic radiation C creates electromagnetic radiation D always reaches the Earth Question The word “encircling” in paragraph is closest in meaning to A attacking B raising C rotating D surrounding Question It is stated in the passage that the ozone layer A enables ultraviolet radiation to reach the Earth B reflects ultraviolet radiation C shields the Earth from a lot of ultraviolet radiation D reaches down to the Earth Question The pronoun “it” in paragraph refers to A radiation B process C formation D damage Question The word “culprits'' in paragraph is closest in meaning to which of the following? A Guilty parties B Detectives C Group members D Leaders Question According to the passage, what happens after a chlorine molecule reacts with an ozone molecule? A The ozone breaks down into three oxygen atoms B Two different molecules are created C The two molecules combine into one molecule D Three distinct molecules result Question The paragraph following the passage most likely discusses A the negative results of the cycle of ozone destruction B where chlorofluorocarbons (CFCs) come from C the causes of the destruction of ozone molecules D how electromagnetic radiation is created ĐÁP ÁN 1-B 2-D 6-B 7-A 3-C 4-A 5-A LỜI GIẢI CHI TIẾT Question 1: Theo đoạn văn, tia cực tím từ mặt trời A gây thiệt hại nghiêm trọng tầng ôzôn trái đất B phần nhỏ xạ điện từ mặt trời C tạo xạ điện từ D luôn đến Trái đất Dẫn chứng: Although only a small percentage of the electromagnetic radiation that is emitted by the Sun is ultraviolet (UV) radiation Question 2: Từ "bao vây" đoạn có ý nghĩa gần với A attacking: công B raising: tăng lên C rotating: xoay quanh D surrounding: xung quanh Question 3: Trong đoạn văn nói tầng ơzơn A Cho phép xạ cực tím đến Trái đất B phản xạ tia cực tím C che chắn cho trái đất khỏi nhiều tia cực tím D xạ lên xuống Trái Đất Dẫn chứng: Fortunately, all of the Sun’s ultraviolet radiation does not reach the Earth because of a layer of oxygen, called the ozone layer encircling the Earth in the stratosphere at an altitude of about 15 miles above the Earth Question 4: Đại từ "nó" đoạn nói đến A Bức xạ B Tiến trình C Sự hình thành D tổn hại Dẫn chứng: When UV radiation is absorbed during the process of ozone formation and reformation, it is unable to reach Earth and cause damage there Question 5: Từ "culprits" đoạn có ý nghĩa gần với câu đây? A Các bên phạm tội B Các nhà thám tử C Các thành viên nhóm D Các nhà lãnh đạo Culprit: tội phạm Question 6: Theo đoạn văn, xảy sau phân tử clo phản ứng với phân tử ozon? A ozon phân hủy thành ba nguyên tử oxy B Hai phân tử khác tạo C Hai phân tử kết hợp thành phân tử D Ba kết phân tử khác biệt Dẫn chứng: The released chlorine reacts with ozone in the stratosphere to form chlorine monoxide (ClO) and oxygen (O2) Question 7: Đoạn văn sau đoạn văn có nhiều khả thảo luận A kết âm chu trình phá hủy ozone B nơi chlorofluorocarbons (CFCs) đến từ C nguyên nhân phá hủy phân tử ozon D làm xạ điện từ tạo Dẫn chứng: the effects of this destructive process are now becoming evident ...D Three distinct molecules result Question The paragraph following the passage most likely discusses A the negative results of the cycle of ozone destruction B where