Final answer:
The committee responsible for reconciling different versions of bills passed by the House and Senate is the conference committee. It is appointed on an ad-hoc basis and produces a unified bill for both chambers to pass.
Step-by-step explanation:
The committee that settles differences between similar bills passed separately by the House and Senate is the conference committee. These conference committees are appointed on an ad-hoc basis when it is necessary to reconcile bills that have been passed in different forms. They are crucial in ensuring that a single unified bill is produced from the disparate versions passed by the respective chambers. Unlike standing committees that handle a specific subject area or joint committees that handle broader issues, the purpose of the conference committee is specifically for the resolution of differences in legislation.
Examples of when conference committees have been bypassed in the legislative process include the Affordable Care Act, where the House deferred to the Senate's version. However, conference committees are typically the norm for most major legislation, such as the Tax Cuts and Jobs Act of 2017.
Therefore, the correct answer to the student's question is d. conference committee.