Answer:
A. The President vetoes bills.
Step-by-step explanation:
Under Article I, section 7 of the U.S. Constitution, the President has the power to refuse to approve a bill -or a joint resolution- in an attempt to prevent its enactment. This procedure is called "veto," and it is restricted to the head of the U.S. federal government, that is the President.
On the contrary, if the President approves the bill, he (or she) signs it into a law.