Which Statement Best Describes the Current Ideological Status of the Congress

Which statement best describes the current ideological status of the Congress?

A) Republicans and Democrats in both the House and Senate have become both more ideologically coherent within their respective ranks and increasingly separated from one another.
B) The ideological distance between the Republicans and Democrats is the smallest in about a century.
C) Roughly 30% of House members and 40% of Senators hold centrist views.
D) Republicans and Democrats in both the House and Senate are internally split ideologically and overlap to a significant degree in the ideological center.