A leading figure in the Scottish enlightenment, Adam Smith’s two major books are to democratic capitalism what Marx’s Das Kapital is to socialism.

1. Adam Smith’s two major books are to democratic capitalism what
2. Adam Smith’s two major books are to democratic capitalism like
3. Adam Smith’s two major books are to democratic capitalism just as
4. Adam Smith wrote two major books that are to democratic capitalism similar to

 e    Adam Smith wrote two major books that are to democratic capitalism what

答案是e,有点不明白e后面what的用法..该怎么去理解