What Did Larry Bartels Find in a Study of Senate

What did Larry Bartels find in a study of Senate roll call votes?

A) Senators are much more responsive to the opinions of affluent constituents.
B) Senators seem to be most responsive to the opinions of middle-class constituents.
C) Senators on the whole display a remarkable lack of interest in public opinion as a driver of their voting policy choices.
D) Senators' voting patterns most strongly correlate with the choices of the president in office.
E) Senators make voting choices primarily based on the opinions of the economic or ethnic class that is most populous in their state.