第一节 语法和词汇知识（共15小题；每小题1分，满分15分）
21. It rains very heavily in this area, which has _______ annual rainfall of 7, 000 mm, _______ideal environment for forests.
A. the; an B. an; 不填
C. an; an D. 不填; the
22. ［2012福州模拟］Time _______ for the trapped miners, so we have to work hard to get them out.
A. has been run out B. is running out
C. is using up D. has used up
23. I will appreciate it if you e-mail the answers to me _______ convenient.
A. when it is B. when you are
C. when it will be D. at your
24. You’ll _______ the department until the end of the year. Next year you will be rearranged.
