Isn’t that your teacher over there?—No, it ______ be him. I’m sure he doesn’t wear glasses.[ ]

What I want to know is _____ he likes the gift given by us.

Messages ______ be changed from sound into electricity before they ______ be sent by radio.

It was a long time before the police________what he was really doing

He expressed his hope _______ he would visit China again the next year, and this was the very hope ______ he expressed as soon as he arrived in the country.