As Incumbents Became More Secure Electorally in the 1960s and 1970s

As incumbents became more secure electorally in the 1960s and 1970s, members of Congress:

A) were able to show more independence from their party in their voting behavior
B) felt that they had to vote with their party in Congress more frequently
C) were able to show more independence from interest groups in their voting behavior
D) felt that they needed to do much less constituent service to the people in their district