Question

谁来帮我解释一下这道英语选择题

Many people have realized that we won't have any more clean water to drink unless something _____ to fight against pollution.

A.was done B.will be done C.to be done D.is done
答案是D 为什么呢？解释详细一点！！

Answer 1

Many people have realized that we won't have any more clean water to drink unless something _____ to fight against pollution.
A.was done B.will be done C.to be done D.is done
答案是D
因为we won't have any more clean water to drink 是将来时态，从句unless 用一般现在时is done表将来。

追问

unless 后面从句一定用一般现在时吗？is done 不是被动语态么？？

追答

unless 引导的条件状语从句用一般现在时表将来。is done 是现在时态的被动语态。句意是：“许多人已经意识到假如不采取行动与污染作斗争，我们将没有更多的饮用的干净水”。

Answer 2

答：时间和条件状语从句中用现在时态表示将来，人称“主将从现”。
例：I will tell him about it if(/when) I see him tomorrow.
本题Many people have realized that 是主句，为现在完成时，不影响that-宾语从句的谓语动词。可忽略不看。只看下一句就行：
We won't have any more clean water to drink unless something _____ to fight against pollution.
unless=if... not...是引导条件状语从句的。
B是将来时，A是过去时，C是非谓语，可排除。
D。是一般现在时的被动语态。
unless sth. is done to fight against pollotion= If sth. is not done to ...
=if we don't do sth. to fight....
译：许多人已经意识到，如果不采取措施与污染作斗争，我们将不再有干净的饮用水可喝。

Answer 3

if/unless的条件句，when等词引导的时间从句中 适用“主将从现”的原则。

本题主干 have realized表明总时态是现在。
realize的宾语从句中，主句是will not （won't）是将来，unless从句中用现在表示将来。
所以只能是D项正确。

本题主要结构
（一级：主句Many people have realized （二级：宾语从句that （三级：主句we won't have any more clean water to drink （四级：条件状语从句unless something _____ to fight against pollution.））））

Answer 4

不好解释，一看就选D 或者是 has been done
估计解释就是won‘t表将来，而something被做是在此之前，故推前语态，一般式和一般完成时都可

Answer 5

水不是现在污染的，一定是已经污染过了，所以要用现在完成时。