The correct answer is D. Senators. U. S. Senators possess two traditional freedoms that no other legislators possess. The aforementioned freedoms are unlimited debate and an unlimited opportunity to offer amendments. Until 1917 these freedoms were subject to very few restrictions, but in 1917 the Senate adopted its first cloture rule (Rule XXII) to end a filibuster (holding the Senate floor to prevent a vote on a bil).
