what引导名词性从句用法：
1.表示“……的东西或事情”：
They’ve done what they can to help her.他们已经尽力帮助了她。
He saves what he earns.他赚多少，积蓄多少。
What Mary is is the secretary.玛丽的职务是秘书。
2.表示“……的人或的样子”：
He is no longer what he was.他已经不是以前的那个样子。
He is what is generally called a traitor.他就是人们通常所说的叛徒。
Who is it that has made Fred what he is now? 是谁把弗雷德培养成现在这个样子的？
3.表示“……的数量或数目”：
Our income is now double what it was ten years ago.我们现在的收入是10年前的两倍。
The number of the students in our school is ten times what it was before liberation.现在我校学生的'数量是解放前的10倍。
4.表示“……的时间”：
After what seemed like hours he came out with a bitter smile.似乎过了几个小时他才苦笑着出来。
The young girl was too frightened to speak, standing there for what seemed like hours.小女孩吓得不敢说话，在那儿站了几个小时。
5.表示“……的地方”：
This is what they call Salt Lake City.这就是他们称为盐湖城的地方。
In 1492, Columbus reached what is now called America.1492年哥伦布到达了现在所称的美洲大陆。