—There is a knock at the door.—---------------?A.who is that

—There is a knock at the door.—---------------?A.who is that there is a knock at the door.it is the second time that some 可以说there is a knock at the door吗 --who's that at the door?--____ is a postman. listen there is a knock at the door 改为同义句 some one is knocking at the door 同义句 —— ——a knock at the doo There is a boy ( )at the door. there is ( ）knocking at the door.GO and see who it is A nobo Who is that at the door? Who is that at the door ？ When you hear a knock on the door,what will you say?用who is 语法,( ) 1 Who's that at the door?____ is the postman.A.She B.