What is one power exclusively reserved for the federal government?

The correct choice is the power of regulating interstate commerce, which is exclusively reserved for the federal government. This power is granted by the Constitution, specifically in Article I, Section 8, and it allows Congress to regulate trade that crosses state lines. This ensures a uniform system of commerce across the entire country, which is crucial for maintaining economic stability and fostering trade relations among the states. The federal government can set regulations to prevent unfair practices and promote competition, which are essential for a healthy national economy.

In contrast, the other options are powers generally reserved for state governments. Conducting elections is predominantly managed at the state level, as states have the authority to determine how elections are run. Establishing schools falls under state control, with states responsible for the education system and its regulations. Issuing marriage licenses is also a state function, as marriage laws vary widely from one state to another, allowing state governments to regulate this aspect based on their legal and cultural contexts.