Only when the villagers were faced with water shortage how serious the problem of water pollution was．
A. did they realize
B. will they realize
C. they did realize
D. were they realized
网友回答
(答案→)A. did they realize
B. will they realize
C. they did realize
D. were they realized
解析：句意：只有在村民面临水资源短缺形势时，他们才意识到水污染是多么严重。考查Only+when从句放在句首时，用部分倒装。