单选21. With the successful

单选21. With the successful
21. With the successful launch of Tiangong-1, which was ___ breakthrough in this field, China’s space dream took a step closer to___ reality.
A. the; aB. a; / C. a; the D. the; /
22. —Oh, how depressed! I’m bound to lose to him in tomorrow’s competition.
—Cheer up! In fact, he is ___ than you.
A. not more nervous B. no more nervousC. no less nervous D. a little less nervous
23. The bus hit against a tree in the fog and ___ to the deep valley,with ten passengers killed
and twenty wounded.
A. down did it rollB. down rolled it C. it down rolled D. down it rolled
24. —Was the driving pleasant when you went to Sichuan last summer?
—No, it ___ for a week when we arrived, so the roads were very muddy.
A. was raining B. has been rainingC. had been rainingD. would have rained
25. Nearly three months had gone by ___ the seriously injured girl showed a slight sign of recovery.
A. until B. after C. since D. before
每个题都要有详解！！！！！！！！！！！！！！