each of the students have their own books 这里谓语为什么要用复数?

问题描述:

each of the students have their own books 这里谓语为什么要用复数?
我也觉得用单数。但是书上专门把这句用红色标出来做特例。但是又不说为什么

用has,因为each是单数.譬如
1) each of you has unique personality.