there is someone in the room,who can it be?请问这句子的someone能换成s

there is someone in the room,who can it be?请问这句子的someone能换成s There is someone in the room.It must be my brother Oh,there is someone in the room. there must be someone in the room _(be)there Someone is knocking at the door.Who can it be?的回答.A.Nothing There's someone outside .Who ---it be A:must B:can C:shall D Oh,there's someone in the room.( )must be my brother A.He B. there is (某人)in the room ,who can it be 根据汉语提示填空.要说为什么? 选择题：-Oh,there is someone in the room. -___ must be my mother there is someone in the room 改否定句 There is someone ringing the door bell.Who _____ it be?A) ca 6.There is someone knocking at the door,who _____ it be?