问题
选择题
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
答案
答案：A
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。