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

Athe majority leader.
Bthe vice president of the United States.
Ca speaker for the house.
Da president pro tem.

Verified Answer :

If you visit the Senate chamber during a session on an average day, you're most likely to find the session presided over by the "majority leader" since this position is almost always only taken by a different person when the leader is unavailable.