在空白处填入适当的代词完成句子和对话.
1.The cat is following me all the time ________ must be hungry.
2.the baby cried all night.I think _________ is sick.
3.—Who's making such a noise?
—________ must be the children.
4.—What's that on the table?
—__________ is a telephone.
5_________ is seven o'clock.I must leave now.