Which of the following is an example of a power exclusive to the federal government?

Establishing a postal service is an example of a power exclusive to the federal government because the Constitution grants Congress the authority to create and maintain a postal system. This power derives from Article I, Section 8, which specifically enumerates the powers of Congress, including the ability to "establish Post Offices and post Roads." This means that only the federal government can manage postal services, ensuring consistency and uniformity across all states.

In contrast, the regulation of education, conducting elections, and issuing marriage licenses are powers that primarily fall under the jurisdiction of state governments. States have the authority to oversee educational institutions, manage election processes, and set criteria for marriage, reflecting the principle of federalism where certain powers are reserved for the states. Hence, the establishment of a postal service stands out as a distinct responsibility of the federal government, emphasizing the unique role it plays in providing national services.