【题目】The boss ______ the worker how to do it, or the accident couldn’t have happened.
A.can’t have told
B.ought to tell
C.could have told
D.mustn’t have told

【答案】A
【解析】从句意看，选项是对过去的否定推测，应该用can’t have done。句意为：老板不可能告诉工人们怎么做了，否则就不会发生事故了。