问题
Have you heard of Loulan?— Of course. It is believed _____ many years ago. [ ]
A: that it covered over by sandstorms
B: that it is covered over by sandstorms
C: to be covered over by sandstorms
D: to have been covered over by sandstorms
B: that it is covered over by sandstorms
C: to be covered over by sandstorms
D: to have been covered over by sandstorms
正确答案是：
