请教关于GWD20-29的语法

Q29:

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

    这个题目的正确答案是E。我也感觉E的句子读起来比较通顺，但是总觉得理不清这个句子结构。正常语序是否 books are what Marx’s Das Kapital is to socialism to  democratic capitalism ? 这是一种什么含义的固定结构吗？

    请各位帮忙解释一下这个用法，多谢！！！

明白了，多谢回答!