A. should study B. should have studied C. must have studied D. must have to study
A. can't have been B. shouldn't have been C. mustn't have been D. wouldn't have been
A. must have sailed B. can sail C. might have sailed D. should have sailed
A. should have been B. must have been C. must be D. should be
A. can't have changed B. wouldn't have changed C. must have changed D. shouldn't have changed
A. needn't go B. had better not go C. should not go D. needn't have gone
A. mustn't go B. shouldn't have gone C. could not go D. couldn't have gone
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