(However)hard he tries,he canhardly avoid making mistakes in her homework,为什么是however?

(However)hard he tries,he canhardly avoid making mistakes in her homework,
为什么是however?

however在这相当于no matter how,无论怎样,“hard he tries”不缺少主语宾语,所以不能用whatever.

however意思是无论如何，作为副词修饰hard
无论他怎么努力

无论他多么努力
”多么“however
放句首起加强语气的作用，however为副词，修饰hard形容词