But for the heavy traffic the police the thieves who tried to escape in the stolen car.

问题补充：

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：

A. would not catch

(答案→)B. couldn’t have caught

C. haven’t caught

D. couldn’t catch

解析：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。