This is my book.改为复数形式 There is a nice cat in the tree.改为复数形式 Those are rulers 单数形式

问题描述:

This is my book.改为复数形式 There is a nice cat in the tree.改为复数形式 Those are rulers 单数形式

These are my books.
There are nice cats in the tree.
That is a ruler.