Here are the correct answers for each question:
1. Peter is the tallest student in my class.
(d. tallest)
2. The deep ocean contains some of the strangest creatures.
(a. strangest)
3. Jane is not so intelligent as her brother.
(c. so intelligent as)
4. He drives as carefully as his father does.
(d. carefully as)
5. What's the best film you've ever seen?
(b. best)
6. Jane is the same as Mary.
(c. the same)
7. I'll be there as soon as I can.
(c. as soon as)
8. Hotels have developed as rapidly as restaurants.
(a. as rapidly as)
9. Commercial centres are more popular than they were many years ago.
(c. more popular than)
10. Computers are considered as modern tools today.
(d. more modern)
11. A supermarket is not so convenient as a shopping centre.
(b. not so convenient than)
12. The return fare costs twice as much as the single one.
(d. twice as much as)
13. Can Tho is farther from Saigon than Bien Hoa is.
(a. farther)
14. Bao Yen sings better than this singer.
(b. better)
15. Jays are shorter and more colorful than crows.
(d. shorter)
16. Ha Noi is by far the most populated city in Viet Nam.
(a. by far)
17. She plays the piano as beautifully as her sister does.
(a. as beautifully)
18. That is his house which is twice as big as mine.
(a. twice as big as)
19. My father is older than yours.
(c. older)
20. HCM city is larger than Hanoi.
(d. larger)