Final answer:
The correct answer to the student's question is option (c): Gave Congress the power to raise an army and navy.
Step-by-step explanation:
The National Government's obligation to protect the States against invasion indirectly arose due to the Constitution's ability to empower Congress with the capability to raise an army and navy. The framers of the Constitution recognized that a unified military force was essential for the survival of the nation, both to defend against foreign threats and to maintain domestic tranquility. The Articles of Confederation had severely limited the central government's ability to respond to such threats by not allowing it to raise its own forces, leaving the responsibility largely to the states. This decentralized approach was found to be inadequate, which led to the Constitutional Convention where a new system was designed to strengthen the national government's defensive capabilities.
Under the new Constitution, Congress was given enough power to "raise and support Armies" and to "provide and maintain a Navy", ensuring that the United States would have a permanent, standing military force at its disposal. This power was a significant departure from the Articles of Confederation, where the national government had to rely on the states for military contributions.
Furthermore, the national government, according to Section 4, committed to protecting all states from foreign military attack and assisting in the case of uprisings or insurrections.