There's a football under the chair变复数

There's a football under the chair变复数 What is under the chair?A.A football B.There is a cat Is there a c__t under the chair There is a cat under the chair. There is a volleyball under the chair.(用she变同义句） there's a man under the tree,改为复数句 There is a mask under the chair.Is it yours?Oh,yes,it's ( ). There(is/are)a cat under the chair under is chair baskball there a the?连词成句 there are some pens under the chair.怎样变单数句啊? There is a book on the chair.(改成复数) There is a dog on the TV.There is a banana under the chair把这