例如 whatever you say is of no use now
这里whatever引导主语从句不能用no matter what 替代
也就是这句“疑问词+ever” 结构除作状语外,还作其他成分.
No matter what happened,he would not mind.=Whatever happened,he would not mind.
这里是做状语
所以什么时候用‘疑问词+ever’都是对的
“no matter+疑问词”要慎用