1, D - flying saucer (=UFO: đĩa bay)

2, A - 10 - 20% (thông tin ở dòng thứ bảy: “Usually 10 - 20% are never identified”

3, D - clouds (thông tin ở hai dòng cuối)

4,  C - Many UFO sightings are hoaxes. (Thông tin ở dòng thứ ba đoạn 2: “Studies also show that very few UFO sightings are hoaxes”)

5, A - explain (figure out: tìm ra, chỉ ra)

6, A - It is any object flying in the sky which cannot be identified by the person who sees it (câu đầu đoạn 1)

7, B - flying saucer (“that” chỉ “flying saucer” được nhắc đến trước đó)

1. D. flying saucer : đĩa bay

2. A. 10 - 20% (Line 7 : “Usually 10 - 20% are never identified”)

3. D. clouds 

4. C. Many UFO sightings are hoaxes. (Line 3 đoạn 2: “Studies also show that very few UFO sightings are hoaxes”)

5. A. explain (figure out: tìm ra, chỉ ra)

6. A. It is any object flying in the sky which cannot be identified by the person who sees it

7. B. flying saucer