--- The accident might not have happened , had we been more careful .
--- But we .
A. didn’t
B. hadn’t
C. weren’t
D. don’t
网友回答
A. didn’t
B. hadn’t
(答案→)C. weren’t
D. don’t
解析：如果我们再小心一些的话事故也许不会发生。根据所给语境might not have happened可知是对过去情况的假设所以知道答语叙述的是过去的事情故选C