This is a key.(改为复数形式）

This is a key.(改为复数形式） Is this her key?怎么改为复数形式? 我父母在第一副相片上怎么说 this is a photo 改为复数句子 school ,key的复数形式 This is a key. （改为复数句） They are a set of_. This is a box.改为复数形式 This is a pen.(改为复数形式) this is a book改为复数形式 This is a cat.(改为复数形式) is that his key (改为复数形式) Is this a bus?(改为复数形式） Those are erasers.(改为单复数形式） This is a leaf.（改为复数形式） This is a soccer ball.（改为复数形式）