the number of books is 20,为什么不是are

A number of the books here ____old. the number of books is 20,为什么不是are a large number of birds是单数复数?the number of books呢? There are a number of books in our library,the number of books is about 5,000(英译中） In a bookstore,the number of Chinese books is 50 more than twice the number of English books.If there are 350 Chinese books,find the number of English books in the bookstore The number of the books in the library reaches.谓语动词是什么? The number of cars is increasing in Beijing.A number of books have been published on this subject翻译 高中英语题record number of books? record number of books were sold,up7.2% from ? year earlier用a或the填,求解释呵呵 英语翻译the number of people who read newspapers or books is declining rapidly翻译 There_____a large number of books in the school library.应该填什么?is;have;has;are the number of books is 20.book不是可数名词吗,为什么用is不用are a number of the number of the number of,a small number of,a number of. the number of造句 the number of造句 the reciprocal of number the number of中文 the number of 是什么意思?