____________ the law should be punished.

①who + ever可引导名词性从句，在主从句中要充当一定的部分。如：
Whoever breaks the rule must be punished.

③no matter + who只能引导让步状语从句。如：
No matter who breaks the rule, he must be punished.

C中 的动词要用原型
No matter who break

You can ask you teacher.

whoever 可以引导名词性从句，在主从句中要充当一定的部分；
而no matter who 只能引导让步状语从句。