Each book____broken down into several units.在空白处应该填is,was,has还是have?为什么?

题目

Each book____broken down into several units.在空白处应该填is,was,has还是have?为什么?

答案

填 is
Each book is broken down into several units.
每本书都被划分到特有的单元.
这是个被动不能用 has,have.这又在说一个现在的状态,用一般现在时.所以填：is.