Question

The manager ______ the worker how to do it, or the accident couldn’t have happened

1. A.
   couldn’t have told
2. B.
   ought to tell
3. C.
   could have told
4. D.
   mustn’t have told

Answer 1

A
考查情态动词的用法：    A. couldn’t have told过去不可能告诉了，B. ought to tell应该告诉      C. could have told本可以告诉却没有告诉，D. must接完成式不用否定，句意是：经理不可能告诉工人怎么做的，否则事故就不会发生了。选A。