The role of the President pro tempore of the Senate is to preside over the Senate in the absence of the Vice President. The President pro tempore is usually the most senior member of the majority party in the Senate and is elected by the Senate. The President pro tempore also has several other responsibilities, such as:
Assigning all joint committee memberships.
Appointing conference committees to resolve differences between the House and Senate versions of a bill.
Signing bills and resolutions passed by the Senate.
Acting as the ceremonial head of the Senate, representing the Senate in official events and ceremonies.
Performing other duties as assigned by the Senate or by Senate rules.
It should also be noted that the role of the President pro tempore is largely ceremonial, and the Vice President of the United States, who is also the President of the Senate, is the one who presides over the Senate proceedings and has more powers and responsibilities.
Explanation: The answer is C, To act as assistant to party leader when needed.