There's someone outside.Who ___it be?

There's someone outside.Who ___it be? There's someone outside .Who ---it be A:must B:can C:shall D I guess there must be someone _ outside the house.Let's stop 1.— There’s someone knocking at the door.Who could _____ be? there is someone in the room,who can it be?请问这句子的someone能换成s 是there must be someone can hear us还是there must someone who c I guess there must be someone( ) outside the house.Let' It's ____comfort to be informed that there's someone . “There will be someone... There will be someone who always be waiting for you,the man There is someone ringing the door bell.Who _____ it be?A) ca I think there will be someone who like you to court you very