Whoever 和Who的区别是什么?

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
句(A) 的正确选项为C.whoever 的含义是：the person who...或anyone who...[无论(不管)是谁],前者特指,后者泛指.句(A)的意思是：无论谁最后离开房间都应该关灯.又如：
Whoever (Anyone who) breaks the law should be punished.不管谁违法都应该受到惩罚.
Whoever (The person who) told you it was lying.无论谁告诉你的都是说谎.
句(B)的正确选项为B.who虽然也可以引导主语从句,但它常保留本身疑问的含义,即“谁”.句(B)的意思为：对我们大家来说,谁给我们讲话还不知道.又如：
Who will go with us has not yet been decided.谁和我们一起去还没决定.
Who will be sent abroad is unknown.还不知道谁将被派往国外.