The　conference——a　full　week　by　the　time　it　ends.A.musted have lasted B.will have lasted C.would last

题目

The　conference——a　full　week　by　the　time　it　ends.A.musted have lasted B.will have lasted C.would last D.has lasted 我想问 by the times it ends 不是说到他结束为止吗?不是将要的意思吗.为什么选B呢?我选的是C.

答案

by the time 到什么时候为止,是一个完成时的标志用语,后接过去的时间,主语用过去完成时,后接现在的时间用现在完成时,后接将来的时间用将来完成时,本句by the time it ends.接的是句子,英文句子——主将从现原则,即主句和状语从句都是将来的动作,状语从句一般用一般现在时表将来,所以虽然是ends,表示的是将来的时间,故主句用将来完成时,意为：这次会议到结束时 将持续一整周.介词by
,by the end of也有类似的用法.例如：We will learned 3000 by the end of next month.
We had learned 3000words by the end of last month.