第二部分英语知识运用（共两节，满分45分）
第一节：单项填空（共15小题，每小题1分；共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. A clean environment can help the city bid for the Olympics, which ______ will promote its economic development.
A. in time B. in turn C. in return D. in fact
22.This bag is twice ______ weight of that one. You’d better carry ______ lighter one of the two.
A. /; / B. a; the C. the; the D. the; a
