If you visit the senate chamber during a session on an average day, you're most likely to find the session presided over by

a. the vice president of the united states.
b. a president pro tem.
c. the majority leader.
d. a speaker for the house.

The vice president of the United States serves as president of the Senate, usually presiding its sessions.

Explanation:

In the absence of the Vice-president of the United States, a president pro tempore is designated.

Usually, the president pro tempore is the most senior member of the majority party, who can either preside the session, or designate a member of the majority party to do so.

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