Why Do Liberal Representatives Largely Come from Liberal Districts and Conservative

Why do liberal representatives largely come from liberal districts and conservative representatives from conservative districts?

A) State legislators know the preferences of every citizen in their state and draw district boundaries to perfectly match this.
B) Representatives poll on every issue and always vote in accordance with the majority opinion from these polls.
C) Political parties perfectly match the liberal-conservative dimension and thus members vote with their party on all votes.
D) Citizens vote for candidates which are most like them, thus producing representatives who share the general majority opinion in districts.
E) Representation is inconsistent, and members simply vote their conscience on every issue in the chamber.