Which of the following is a main duty of the United States Congress?

• A. Enforcing federal laws
• B. Interpreting the Constitution
• C. Declaring war
• D. Issuing executive orders

Answer: (C)

The key idea here is the constitutional power to declare war. Congress holds the authority to officially declare war and to raise and support the armed forces, reflecting a deliberate check on the use of military force. The President may command the troops as Commander-in-Chief, but a formal declaration of war—authorizing the nation to enter a state of war and often enabling funding for the effort—rests with Congress. This division of power ensures that starting a major conflict requires legislative approval and funding.

The other options align with different branches: enforcing federal laws is done by the executive branch, interpreting the Constitution is the judiciary’s role, and issuing executive orders is a presidential power. Therefore, declaring war is the main duty among the choices because it is the explicit constitutional prerogative of Congress.