1. who与whoever
who 和whoever都可以引导主语从句，只能置于句首，不能用形式主语it代替。它们也都有"谁"的含义， 但能否互相替代呢？请观察下列句子并选择正确选项：
(A) ________ leaves the room last ought to turn off the light.
A. Anyone B. Who C. Whoever D. No matter who
(B) ________ will give us a talk is unknown to us all.
A. Whoever B. Who C. Anyone D. No matter who
