The large size and roughly circular shape of the Pacific made some scientists think that it ______ a hole left when the moon separated from the earth.

A．used to be

B．would have been

C．might have been

D．should have been

腹外疝嵌顿是指（）

A.所有不能回纳的腹外疝

B.内容物与疝囊粘连的腹外疝

C.疝囊颈弹性收缩将内容物卡住的腹外疝

D.肠管成疝囊一部分的腹外疝

E.以上都不是