Choose the correct options

1. They have just moved to this city. It must
   [be|have been]
   very unusual for them here now.
2. Probably his account was hacked. He can't
   [send|have sent]
   such a message.
3. Why are there so many people near this shop? Something might
   [happen|have happened].
4. You probably know this actress. You could
   [see|have seen]
   her in many music shows on TV.
5. You can't
   [go|have gone]
   outside unless you finish all your homework.