This is a pen 变为复数如题

This is a pen 变为复数如题 This is a pen变为复数句,怎么变 That is a pen.(变为复数) that is a pen (变为复数） this is a pen.改为复数句 This is a pen.(改为复数形式) there is a pen on the desk 变为复数 this is a bus.【变为复数句】 This is a key.(变为复数) This is pen变复数 Is this a pen?（变复数句） Is this a car?复数Is this a car?(变为复数） Yes,it is.（变为复数） this is a boy is schoolbag 变为复数形式 What is this It is a photo.变为复数形式 This is a pair of glasses 变为复数 This is his pen.复数形式 this.is pen变复数句 1 This is {a red pen.}( 对括号里的进行提问）2 This ruler is {yellow.}(同上）3 It's a green watch.(变为复数形式)