Half of the class ___ most of the work,The rest ___ really difficult.

问题描述:

Half of the class ___ most of the work,The rest ___ really difficult.
a.has done; are b.has done; is
c.have done; is d.have done; are
应该选什么 、为什么

Chalf of the class表示学生 复数用have done
the rest 表示 the rest of the work表示单数 用 is