What his last name 这句话哪里错了

问题描述:

What his last name 这句话哪里错了

这是一个主语+系动词+表语的疑问句,这里没有系动词be.
应该是What is his last name.

少了be动词
加is
What is his last name ?

没有谓语动词,应该是
What is his last name