What does the term "instrumentalities of interstate commerce" refer to?

The term "instrumentalities of interstate commerce" encompasses various means and methods utilized for the transportation of goods and services across state lines, which is crucial for the functioning of a national economy. This term is generally interpreted to include vehicles such as trucks and planes, which are essential in the movement of goods between states.

In the context of federal regulation, particularly under the Commerce Clause of the U.S. Constitution, instrumentalities of interstate commerce can extend to any methods of conveyance that facilitate trade and communication across state boundaries. Trucks deliver goods directly from one state to another, while planes transport not only cargo but also passengers, thereby playing a significant role in interstate economic activities.

This interpretation aligns with the broader understanding of what constitutes instrumentalities of interstate commerce, which is grounded in their direct involvement in facilitating interstate movement. Therefore, vehicles like trucks and planes are rightly categorized as instrumentalities of interstate commerce, making this the correct answer.