What are the limits of the president's power to pardon?

The president's power to pardon is indeed limited primarily to federal offenses. This power is vested in the Constitution, specifically in Article II, Section 2. It grants the president the authority to grant reprieves and pardons for offenses against the United States, thereby indicating that the pardoning power is applicable solely at the federal level.

Thus, while the president can pardon individuals for federal crimes, this power does not extend to state offenses. State governments have their own systems for dealing with pardons that are independent of federal authority. The exception would be civil contempt charges, which could be interpreted in some contexts as falling under the ambit of the president's power; however, civil cases generally do not involve the same level of criminality that warrants pardoning.

In essence, the correct answer reflects the understanding that the president’s clemency powers function within specific limitations, reinforcing the separation of powers with respect to state and federal jurisdictions in the legal system.