What are the 3 purposes of the committee system

Congressional committees fall into four categories: standing, select, joint and conference committees. All four types of committees accept bills and ultimately decide whether to turn them into laws. The committees share this responsibility, but have different roles. Standing committees typically outlast congressional appointments and may retain members through multiple congressional elections. Standing committees evaluate and shape draft laws, and may perform investigations, too. Select committees typically form for short periods of time. Unlike standing committees, they do not draft legislation. Select committees form primarily to undertake investigations surrounding political events, such as scandals and assassinations. Joint committees contain members from the House and Senate. These committees perform similar functions as select committees. They also facilitate communications between the House and Senate to help coordinate actions. Lastly, conference committees form when the House and Senate disagree about the content in individual bills. Conference committees bring members of the House and Senate together to revisit the original bill and create mutually agreeable changes to allow those bills to pass.

The answer would be a