Earth is believed _____ by an object the size of Mars at some point in the distant past before its surface cooled. A. to be hit B. to have hit C. to have been hit D. to hit --优优班--学霸训练营

Earth is believed _____ by an object the size of Mars at some point in the distant past before its surface cooled.

A. to be hit
B. to have hit
C. to have been hit
D. to hit

【考点】不定式的完成式,不定式的被动式

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难度：中等

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