问题
选择题
But for the heavy traffic, the police ___ the thieves who tried to escape in the stolen car.
A．would not catch
B．couldn’t have caught
C．haven’t caught
D．couldn’t catch
答案
答案：B
考查虚拟语气。根据句中but for (要不是)得知条件，要不是交通繁忙，警察就不能抓住企图逃跑的贼了。couldn’t have done 本不能做……却做到了。