---Do you know the books on the shelves?
--- Sorry, I can’t count them, because there are books.
A. a number of; the number of B. a number of; a number
C. the number of; a number of
网友回答
解析：a number of一些，许多；the number of……的数目。句意：你知道书架上书的数目吗？——对不起，我不能数出他们，因为有许多书。故选C。