a cat's litter tray的用法和样例：
- Our cat has a litter of four kittens.
- She set a tray down on the table.
- Even abe smiled, but only a litter and not for long.
- Her desk was covered in a litter of books and papers.
- There is a vein of melancholy in his character.
- There was a long lag in forwarding mail to us.