This is a bat.怎么改为复数形式

This is a bat.怎么改为复数形式 this is a man 改为复数怎么写 is this a car?改为复数形式怎么改? This is a backpack(改为复数句子)怎么改? It is a baseball bat.改复数 This is a book 改为复数句 This is a pear.改为复数句 this is a book改为复数形式 This is a dress.改为复数形式 this is a tree 改为复数句 Is this a bus （改为复数句 This is a bus.改为复数. this is a shirt改为复数句 this is a strawberry改为复数 This is a young tree.(改为复数) this is a watch(改为复数句) This is a knife 改为复数 This is a cat.(改为复数形式)