废寝忘食 历史名人:·6.Not until all fish died in the river ___ how seriousness the pollution was.

a
not until．
直到...才(在...以前不)在句首时后用倒装语序；在句中不用倒装．

例句与用法:
1. It was not until he came that I left.
直到他来我才离开。

2. Not until eleven o'clock did he come home.
他到十一点才回家。

3. I don't know whether we will start the job or not until I see how the land lies.
在没有分析情况之前，我不知道是否要开始这项工作。

4. Not until last night did I get the news.
直到昨晚我才听到这消息。

5. Not until his friend offered to help could he do it.
他的朋友帮助他，他才有办法做那事。

6. Not until a few months later did he know the story.
直到几个月后，他才知道这故事。

7. It was not until a few months later that he knew the story.
直到几个月后，他才知道这故事。

8. It was not until he got seriously ill that he knew the importance of health.
直到他生了重病，他才知道健康的重要。

a
not until后接倒装
所以是
NOT UNTIL all fish died in the river DID HE REALIZE how seriousness the pollution was

A

正常顺序是he didn't realize how....was until all...

not..until...知道什么时候才..

not until.提前.则语序变为 DID HE REALIZE倒装句

C.he did realize
他意识到了a和b都没法解释
用排除法选c

A, 是个倒装句.有not...until在句首的句字要倒装,类似的有never,hardly,等否定意义的词在句首都要倒装,倒装句分很多种类型.eg:high he jumped.我也一时说不全