- Someone is knocking at the door.  - It ______ be Tom. He is still in the school.

These broken pieces of plates don’t fit together, they ___________ parts of different ones.

– Whose ping pong bat is this? -- I’m not sure. I think it ______be Tom’s.

—Could I surf the Internet for twenty more minutes, Mum?—Oh, dear, if you________.

 -- Whose French book is it?-- It __________ be Lucy’s. Look! Her name is on the book!