书上说是“Classes begin at eight.She has four classes in the morning.”

问题描述:

书上说是“Classes begin at eight.She has four classes in the morning.”
我疑惑为什么不是"Class begin"和"four class in the morning".

Classes begin,从语法说是对的,从意思上说是:课堂时间是8点开始.classes在这里是统称,指课堂,泛指,没有特指某一节课.所以用复数.four classes指4节课,可数名词,用复数形式.