Question

in the vice presidents absence, the presiding officer of the senate is the
president pro tempore.
speaker of the senate.
dean of the senate.
majority floor leader.

Explanation:

In the United States, the vice - president is the presiding officer of the Senate. In their absence, the president pro tempore presides over Senate proceedings. There is no "Speaker of the Senate", "Dean of the Senate" is not a presiding role, and the majority floor leader is focused on party strategy and not presiding in the vice - president's absence.

Answer:

A. president pro tempore