a litter tray的用法和样例：
- Our cat has a litter of four kittens.
- His dog hasn't had a litter of puppies.
- Even abe smiled, but only a litter and not for long.
- Her desk was covered in a litter of books and papers.
- The cat dropped a litter of four kittens.
- The desk was covered with a litter of documents.
a litter tray的相关资料：
a gogo a A sparsely inhabited rural region. a crackajack at technical innovation a rigorous analysis/investigation a predisposition towards melancholia A delicious or invigorating drink. A spectrum of educational activities A Novel Polarization State Generator a submarine for research purposes. a convoluted argument/explanation