who can it be at the door?

Someone is knocking at the door.Who can it be?的回答.A.Nothing someone is knocking at the door.who [ ]it be? ---someone is knocking at the door.Who _____ it be? Someone is knocking at the door.Who it be?— It be Tom.He is -Who ＿＿it be that is knocking at the door -It＿＿b Someone is knocking at the door,but who can （ ）be.A one B he —There is somebady at the door.Who _____ it be? 6.There is someone knocking at the door,who _____ it be? Someone is knocking at the door,but who can____ be? --Listen! Someone is knocking at the door. Who _____it be? ---Listen! Someone is knocking at the door. Who _____it be? A knock on the door!Who --it be?