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，满分15分）
21．________ with the size of the whole earth, the biggest ocean does not seem big at all.
A. Compare B. When comparing
C. Comparing D. When compared
22．It was 1969___ the American astronauts succeeded in landing on the moon.
A. that B. when C. on which D. which
23．It was ______ back home after the experiment.
A. not until midnight did he go B. until midnight that he didn’t go
C. not until midnight that he went D. until midnight when he didn’t go
24．There's some doubt ____he'll keep his promise.
