21.在你告诉我之前，我对此事一无所知。

　I was ____ _____ _______about it before you told me.

20. Seeing the frightening flood, they were ______taking the boat.

[完成句子]

(根据汉语提示完成句子)。

19. The happy moment we ________________________________will soon come.

18. The terrorists __________that they were responsible for the bombing.

17. In ability, Mike _________above the rest of the students in his class.

16.____________ by trees, the lake looks more beautiful.

15. We __________the most important scientific development of the century last month.

14. I shall always _________the memory of our meetings.

13. Every day, mainland China _______Hong Kong with lots of vegetables.

12. __________and consider the advantages of living in a larger house!