Which of the following is an example of expressed powers?

Expressed powers are those specifically granted to the federal government by the Constitution. They are clearly outlined and defined, allowing for a precise understanding of what the government is authorized to do.

Establishing a postal system is a prime example of an expressed power because the Constitution explicitly grants Congress the authority to "provide for the Punishment of counterfeiting the Securities and current Coin of the United States; To establish Post Offices and post Roads." This clear wording in the Constitution allows for no ambiguity regarding the federal government's ability to create and maintain a postal system.

In contrast, other options represent powers that are either implied or reserved. The regulation of interstate commerce is often emphasized as an implied power derived from the Commerce Clause, which allows for broader interpretations. Governing local governments typically falls under the purview of state powers, not federal. Creating a state currency is also not an expressed power, as only the federal government has the power to issue legal tender, further solidifying why the choice related to establishing a postal system is the correct answer.