How many are there in the school?A. librarysB. classesC. glassD. grade

问题补充：

How many are there in the school?

A. librarys

B. classes

C. glass

D. grade

答案：

A. librarys

(答案→)B. classes

C. glass

D. grade

解析：how many后接可数名词的复数形式，故选答案为B，A项复数形式不对。