The correct answer is "A".
A line-item veto is a form of veto that enables the President of the United States to reject certain provisions of a bill which has reached his instance. However, this veto does not reject the entire bill.
During 1994, Republican senators, which at the time were the majority, were intending to pass certain legislation aligned to their "Contract with America" proposals. However, President Clinton made use of the line-item veto in order to hinder many of these efforts. This caused Republican Senators to decided to initiate a lawsuit in order to prevent the line-item veto.
The Supreme Court would eventually rule in favor of the senators, arguing the line-item veto Act of 1996 violated the United States Constitution because it gave the President the power to unilaterally amend parts of bills which had passed through the entire legislative process.