题目内容
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
B. to have hit
C. to have been hit
D. to hit
C
练习册系列答案
相关题目
The origin of ____ life on earth is ____ question that interests astronomers.(原创)
A.the; the |
B.\; a |
C.\ ; the |
D.the; a |