Choose the correct modal constructions.

Choose the correct option.

Nobody knows what happened to Lenny. I think it [will be|might have been|should have been] a road accident.

Troy [should have studied|studied|must study] harder before the test. Now he has to retake it.

My mum is so excited! She [should have passed|must have passed|can't have passed] her Spanish exam.

Alex [can't have travelled|might travel|should have travelled] abroad on his last vacation. His international passport has recently expired.

The teacher explained the task, but Helen completed it incorrectly. She [mustn't have misunderstood|should have misunderstood|must have misunderstood] the explanation.

You [should have cooked|needn't have cooked|must have cooked] so much food; we're on a diet.