18.

29. When Alexander Fleming discovered the first antibiotic, he ______.

10. ______ many times,he finally understood it.

8. It is no longer a problem ______ the poor children in this district can go to school.

15. ---Betty was feeling pretty blue for a while, but she’s better now.---_______.

荀子曰： “不闻不若闻之，闻之不若见之。”这句话所体现的教学原则是（  ）。

9. Time becomes scarce; new friendships are often _____ on sharing the burden of child care.

13. ______ all our efforts, we still lost the game.

20.

28. It is clear that ______.

21.

4.开学考试成绩能够预测入学学后的学业成绩，这说明该测验具有较高的（ ）。