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.

the berlin blockade was an international crisis that arose from an attempt by the soviet union, in 1948–49, to force the western allied powers (the united states, the united kingdom, and france) to abandon their post-world war ii jurisdictions in west berlin. in march 1948 the allied powers decided to unite their different occupation zones of germany into a single economic unit. in protest, the soviet representative withdrew from the allied control council. coincident with the introduction of a new deutsche mark in west berlin (as throughout west germany), which the soviets regarded as a violation of agreements with the allies, the soviet occupation forces in eastern germany began a blockade of all rail, road, and water communications between berlin and the west. on june 24 the soviets announced that the four-power administration of berlin had ceased and that the allies no longer had any rights there.

yup! you are correct it is b.