What Is the Best Explanation for Liberal Representatives Largely Coming

What is the best explanation for liberal representatives largely coming from liberal districts and conservative representatives from conservative districts?

A) Citizens vote for candidates that are most like them, thus producing representatives who share the general majority opinion in districts.
B) Representatives poll on most issues and typically 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) State legislators know the preferences of citizens in their states and draw district boundaries to match these preferences.
E) Representation is inconsistent, and members simply vote their conscience on every issue in the chamber.