The state may undertake what when repelling invasion, suppressing insurrection, and defending the state in times of war?

The correct answer is rooted in the powers granted to state governments for addressing emergencies and ensuring public safety. When dealing with situations like invasion, insurrection, or war, a state may need the capability to incur debt. This ability allows the state to finance immediate and necessary expenditures, such as mobilizing the National Guard, ensuring public safety, and providing relief services without delay. Engaging in debt can be essential for swift action during crises where traditional funding sources may not be immediately accessible or sufficient.

In contrast, while taxation is a common method for generating revenue, it typically entails a longer process of legislative approval and collection, which may not be feasible during urgent situations. Legislation, while crucial for governing, involves a deliberative process that may not provide the immediate response required in emergencies. Emergency powers, while relevant, generally refer to the broader authority that governments can exercise under extraordinary circumstances but do not specifically highlight the financial mechanisms available, such as incurring debt, that can facilitate rapid action and response to threats.