Loulan is believed over by sandstorms gradually from AD200 to AD400.
A. to cover
B. to be covered
C. to have covered
D. to have been covered
网友回答
A. to cover
B. to be covered
C. to have covered
(答案→)D. to have been covered
解析：考查句型：sb/sth is believed to do/to have done,据相信某人/某物…，如果是将要做，用不定式一般式to do如果是已经做了，用不定式的完成式，句意：大家相信楼兰是从公元前200年到公元前400年逐渐被沙尘暴淹没的。因为楼兰是被掩埋的，用不定式完成式的被动，选D。