将来完成时的一道选择题Before the end of nineties,air pollution ( ) a serious problem that endangers the health of the human race.A.will be become B.will becomeC.will have becomeD.will have been become

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将来完成时的一道选择题Before the end of nineties,air pollution ( ) a serious problem that endangers the health of the human race.A.will be become B.will becomeC.will have becomeD.will have been become
将来完成时的一道选择题
Before the end of nineties,air pollution ( ) a serious problem that endangers the health of the human race.
A.will be become
B.will become
C.will have become
D.will have been become

将来完成时的一道选择题Before the end of nineties,air pollution ( ) a serious problem that endangers the health of the human race.A.will be become B.will becomeC.will have becomeD.will have been become
在九十世纪末的时候,空气污染将会成为一个威胁人类健康的严重问题.
首先,空气污染是自己成为一个问题而不是被成为一个问题,所以不能用被动,所以先排除A、D,然后,九十世纪末还没到,是表示一个将来的时间状语,所以要用将来时态,再次,整道题的意思是过去某个时候开始到九十世纪末为止这一段时间内,空气污染成为问题.所以要用完成时态,所以总的就要用将来完成时态,所以选C

做这种题最重要的就是看懂句意,首先air pollution 后面不能是被动,不然说不通,所以排除A D 再来看B项与C项 C项更好,因为前面有before在...时候之前应该已经完成了。这个句子是站在将来的时间上说的,如果较真的话,B项也是对的,但是C项最好