... essential to (C) the study of (D) engineering.68. Laser discs (A) provide images of (B) best quality than (C) those of (D) either television signals or video tapes.69. (A) Some metals (B) such gold, ... mistake (A, B, C, or D).66. School children in (A) the same grade in (B) Vietnamese schools (C) are usually (D) the same old as their classmates.67. (A) An understand of calculus (B) is essential ... silver, copper, and tin occur (C) naturally, and are easy (D) to work.70. (A) According to a team of (B) scientists, (C) there are evidence that Mount Everest is still (D) rising.3...