It is believed to over by sandstorms from AD 200 to AD 400.A．gradually cover B．b
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It is believed to _____ over by sandstorms from AD 200 to AD 400.
| A．gradually cover | B．be gradually being covered |
| C．have been gradually covered | D．be gradually covered |
试题答案
C
解析试题分析:句意：人们都认为它是在公元200年到公元400年期间被风沙逐渐覆盖的。固定句型：sb is believed to do “人们认为……”，相当于it is believed that +从句，故答案选C。
考点：考查非谓语动词。