The correct answer is "C. Conference Committees".
These are committees appointed by the US Congress in order to resolve disagreements over the same bill. These differences occur due to the numerous amendments that are applied to the bill in the hearings which occur in both chambers. Draft versions of bills are passed along both houses and these are in their legal authority to be in disagreement over the bills. The house that produces the bill can either elaborate a new draft or be in disagreement over the position of the other house to reject the draft. If the latter happens, then both houses will have to form a conference committee in order to elaborate a single draft of the bill.
