问题补充:
Only when the firefighters put off the firewhat great damage it caused.
A. we had realized
B. had we realized
C. we realize
D. did we realize
答案:
A. we had realized
B. had we realized
C. we realize
(答案→)D. did we realize
解析:句意:当消防队员扑灭火的时候我们才意识到这场大火引起这么大的灾难。这里是倒装,only+状语放在句首时主句的谓语动词用部分倒装,,又因为从句用的是过去式,故主句用一般过去式,故选D。