第一节：单项填空（共15小题；每小题1分，满分15分）
从A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
21. Without _____thorough understanding of China’s specific conditions, you can’t have ______ say over the only-child policy.
A. a; the B. the; a C. a; a; D. the; the
22. —What did the professor ask us to do just now?
—Sorry, I about my trip to the Wolf Hill at the weekend.
A. had thought B. thought C. think D. was thinking
