Why do Senators have the ability to block hearings for Presidential appointments?

Article II, Section 2, of the Constitution provides that the President shall appoint officers of the United States “by and with the Advice and Consent of the Senate.” This report describes the process by which the Senate provides advice and consent on presidential nominations, including receipt and referral of nominations, committee practices, and floor procedure.

Committees play the central role in the process through investigations and hearings. Senate Rule XXXI provides that nominations shall be referred to appropriate committees “unless otherwise ordered.” Most nominations are referred, although a Senate standing order provides that some “privileged” nominations to specified positions will not be referred unless requested by a Senator. The Senate rule concerning committee jurisdictions (Rule XXV) broadly defines issue areas for committees, and the same jurisdictional statements generally apply to nominations as well as legislation. A committee often gathers information about a nominee either before or instead of a formal hearing. A committee considering a nomination has four options. It can report the nomination to the Senate favorably, unfavorably, or without recommendation, or it can choose to take no action. It is more common for a committee to take no action on a nomination than to reject a nominee outright.

it was douglas macarthur..

may i ask which amendments?