how hard he works for you is 语法有错误吗?

不一定啊,假设句子还有后面的补充,加入条件或形容词等,就不会有语法错误啊。例如：How hard he works for you is totally up to his mind。How hard he works for you is admirable。如果句子就这样“how hard he works for you is。"就有些问题了。