在空白处填入适当的代词完成句子和对话.
1.Thecatisfollowingmeallthetime________mustbehungry.
2.thebabycriedallnight.Ithink_________issick.
3.—Who'smakingsuchanoise?
—________mustbethechildren.
4.—What'sthatonthetable?
—__________isatelephone.
5_________isseveno'clock.Imustleavenow.