Though the constitution dictates that the vice president is the leader of the senate, the day-to-day leadership falls to what position?
a) speaker
b) party whip
c) majority leader
d) president pro tempore

The correct answer is D. Though the Constitution dictates that the Vice President is the leader of the Senate, the day-to-day leadership falls to the President Pro Tempore.

Explanation:

President Pro Tempore is a senior member of the United States Senate, the chairman of the Senate in the absence of the President-in-Office, the Vice-President. The Senate elects the President Pro Tempore, who normally is the member of the Senate-majority party who has the longest uninterrupted career as a senator.

President Pro Tempore is third in the presidential line of succession after the Vice President and the Speaker of the House of Representatives.