Which power is granted by the U.S. Constitution to both federal and state governments concurrently?

The correct selection involves the power to impose taxes, which is a concurrent power shared by both federal and state governments. This means that both levels of government can levy taxes on individuals and businesses within their jurisdictions to fund various services and programs.

The power of taxation is fundamental to any governing body, as it generates revenue necessary for essential functions such as infrastructure, education, public safety, and welfare programs. The U.S. Constitution explicitly allows states to collect taxes, and at the same time, the federal government has broad authority to tax in order to meet national needs.

Other options listed indicate powers that are specifically allocated to one level of government. For instance, regulating immigration is primarily a federal responsibility, as it pertains to national borders and the admission of foreign nationals. Control over foreign trade is also reserved for the federal government, as trade agreements and tariffs involve international relations. Establishing postal services is exclusively a federal power, as the U.S. Postal Service operates under federal law.

Thus, the ability to impose taxes represents a key aspect of government function that underscores the overlapping authority at both federal and state levels, making it the correct answer.