Final answer:
The correct answer is c. Title 32 of the United States Code. This title establishes the procedures for Congress to order the National Guard and militia units into active Federal duty, in accordance with the powers granted to Congress under the U.S. Constitution.
Step-by-step explanation:
The procedures and circumstances for Congress to order units into active Federal duty are established in United States Code (USC) Title 32. This means that the answer to the question is option c. Title 32 of the USC outlines the role of the National Guard and the militia when called into federal service. It encompasses the powers provided to Congress under Section 8 Clauses 15 and 16 of the U.S. Constitution, which give Congress the authority to call out the militia and govern its actions, including how its members are trained and the appointment of officers.
Under these clauses and Title 32, Congress has the power to decide on funding for military actions and to maintain control over the militia when they are called into federal service. Moreover, the president has the ability to engage the military and can send troops to other countries but must seek congressional approval to continue beyond 60 days, as per the provisions outlined around the president's role in military affairs.