1) It must be David who is calling.now.
2) Anna should be winner tomorrow.
3) This letter could be from my cousin.
4) It can't be Colin knocking at the door.
5) She must be going to a fancy-dress party.
6) The hairbrush might be in the living room.
7) Harriet should be there in half an hour.
8) James could be in trouble at school/