Oh, there is someone knocking at the door. — __________ must be your neighbour, Mrs Black.

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

Where is Mr. Zhang? –He _________ for two days. Can I give him a message?

Can you ______who has lost the watch?

Is the door_____now? It’s so cold.—Sorry,I will keep the door________.