Evidence has been put forward showing that astronauts exposed to _英语解答

Evidence has been put forward showing that astronauts exposed to long periods of weightlessness _ quite severely.
A.have affected
B.had affected
C.have been affected
D.had been affected
答案是选c,为什那么不用用had而用have

人气：140 ℃　时间：2019-10-23 14:05:06

解答

.显然是have,它在描述一种事实,而不是完成的时态,你可能看到了exposed这个词,但是这不是过去式,你去查下字典就知道了,又不是加了ed就代表过去式