1.energy 2. stomachs 3. ripe 4. paces 5. chemistry; chemical 6. now and then 7. keep up with 8. make a choice 9. digest 10. sleepy 11. soft 12. balance 13. tasty 14. boils 15. organic 16. diet 17. gained 18. function 19. mixture 20. suggestion

Unit 14：

20.　 When we are in Beijing, they gave an ___________(招待)to us.

Unit 13

19.　 No country should neglect the e_________of its young people.

18.　 She is interested in __________(环境保护).

17.　 The ________(文明)of mankind has taken thousands of years.

16.　 All eyes were f________on the speaker.

15.　 He gave me an apple in ________(交换) for a cake.

14.　 There is a l______to everything; you should not always act like that.

13.　 The enemy tried to c______off our way back, but didn’t succeed.

12.　 Everyone who has been to the Tian’anmen Square can’t help ______(赞赏)it.