Use the correct form of the words in parentheses:
11. Minh Tuan met his old friend while he..................in Nha Trang (work)
12. Yesterday we ......................five minutes late. (arrive)
13. Flowes should ...............in warm places. (keep)
14. What makes you............... in the existence of UFOs? (believe)
15. Many new cars have much lower fuel.................... (consume)
16. We have a fierce..............in our traditions. (proud)
17. It was very ................of you leave matches where children could get them. (care)
18. He enjoys the constant..................... with students from other classes (interact)
19. The palace was.................. damaged by the fire. (extend)
20. Some .................groups have declared a boycott of tourism on the island (environment)