Choose the correct answer

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1. She always does really well on exams. She __________ a lot.
A. must study B. might study C. can't study

2. Alex: Where's John?
Ben: I'm not sure. He __________ in the teacher's office.
A. can be B. might be C. must be

3. I'm not very sure. I think he __________ right.
A. could be B. must be C. mustn't be

4. Anna: 'Did you know that he works every weekend?'
John: 'Really? That __________ healthy.'
A. may be B. must be C. can't be

5. I can't find my books. I __________ them at home this morning.
A. could have leave B. might have left C. can't leave

6. I am sure he was here. I saw his car in front of the building. He __________ here.
A. must be B. might have been C. must have been