Not until all the fish died in the lake how serious the pollution was.A. did the villager

问题补充：

Not until all the fish died in the lake how serious the pollution was.

A. did the villagers realize

B. the villagers realized

C. realized the villagers

D. do the villagers realize

答案：

(答案→)A. did the villagers realize

B. the villagers realized

C. realized the villagers

D. do the villagers realize

解析：句意：直到湖里所有的鱼都死了，村民才意识到污染多严重。Not until+从句放在句首的时候，后面的主句要部分倒装，助动词放在主语前面，排除BC，因为前面用died，所以用一般过去式，选A。