Fill in: must, can't or may.

1 That man over there ....... be Tom. He's abroad at the moment.
2 Helen ........ have called earlier. I'm not really sure.
3 Jane's not online, so she .... have turned off her computer.
4 Kate ......... have been chatting
online. She doesn't even have the Internet!
5 Steve ................ be watching a film now. I'm sure of it!​