Answer: C. preside over the Senate.
Other than being a suitable replacement for the President in certain situations and the principal advisor to the president, the Vice President is also an officer of the legislative arm of government acting as the president of the senate. With this, the Vice President can preside over the Senate at any time. The Vice President, however, will not vote unless during a tie-breaking vote. The Senate President pro tempore presides over the Senate only when the Vice President is unavailable.