Which of the following is an example of a power given to Congress by the commerce clause?

The power given to Congress by the commerce clause specifically concerns the regulation of commerce among the states, as well as with foreign nations and Indian tribes. This clause is a fundamental component of the Constitution, found in Article I, Section 8, and it grants Congress the authority to create laws that govern trade and economic activities that cross state lines.

Regulating interstate trade falls directly under this provision because it involves overseeing the economic interactions that happen between states. This helps to ensure a cohesive economic environment across the nation, allowing for a free flow of goods and services, which is essential for the functioning of a national economy.

Establishing post offices, declaring war, and issuing patents, while important powers of Congress, do not stem from the commerce clause. Instead, these actions are supported by different powers granted in the Constitution. For example, establishing post offices is rooted in the power to "to establish Post Offices and post Roads," while the power to declare war comes from the authority to raise and support Armies and navies. Issuing patents is derived from the power to promote the progress of science and useful arts. Thus, the correct option emphasizes the specific responsibility of Congress in relation to commerce, highlighting its essential role in regulating trade and economic relations.