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
网友回答
(答案→)A. can't have told
B. ought to tell
C. could have told
D. mustn't have told
解析：抓住关键“or”，意为“否则”，所以前后意思相反。