1. Jack ........... be at home. His jacket is still here.

CAN´TCAN´T

a) might b) can't c) mustn´t

2. I .......... still have your book, but I'm not certain.

MIGHTMIGHT

a) might b) must c) can't

3. This ....... be the right answer. The others are definitely wrong.

MUSTMUST

a) can't b) must c) could

4. That ............. be Maria. I'm sure she's got blond hair, not dark. 

CCAN´T

a) may b) might c) can't

5. I'm not sure at all but the painting .......... be an original.

MIGHTMIGHT

a) might b) must c) can't

6. He's been working hard so he ........... be tired.  

MUSTMUST

a) may b) can't c) must