Final answer:
Congress is responsible for enacting fiscal policy in the United States, which includes decisions on government spending and taxation. The answer is option D.
Step-by-step explanation:
The entity responsible for enacting fiscal policy in the United States is Congress. Fiscal policy pertains to government spending and taxation decisions which are controlled by the legislative branch of the government.
While the Federal Reserve, often referred to as "the Fed," has the power to set and implement monetary policy, such as managing interest rates and credit conditions, it operates independently from Congress and does not enact fiscal policy. The Fed's ability to act quickly and its significant impact on the economy through monetary policy is part of its unique attributes as the central bank of the United States.