A federal statute imposed criminal penalties for killing certain specified animals that have been determined by Congress to be of importance to the tourism industry in the region in which the animal was located. Among the animals protected was the red fox. However, a state in which the red fox was located classified the animal as a varmint that could be destroyed at will by anyone with a general hunting license. A rancher who possessed a valid state general hunting license regularly shot and killed red foxes that ate his artichoke plants. If the rancher is prosecuted under the federal statute and challenges the constitutionality of the law, which of the following is the strongest constitutional argument in support of the federal statute?

a. The commerce power.
b. The Necessary and Proper Clause.
c. The police power.
d. The power to regulate federal lands.