The work ___A____ by the time you get there.

问题描述:

The work ___A____ by the time you get there.
A. will have been done B. is doneC. had been doneD. would have
请高手讲下其中的语法知识,再翻译下,我将感激不尽!为什么要选A.谢谢!

因为句子中有明显表明时间的词语by
一般看到by the time就两种时态:过去完成时和将来完成时
by the time后面为一般现在时,说明事情还未发生,所以用将来完成时
也就是A