What defines a trailer in transportation terms?

A trailer in transportation terms is defined as a vehicle designed to be towed by a motor vehicle, which aligns with the characteristics conveyed in the correct choice. This definition emphasizes that a trailer is not equipped with its own engine or means of propulsion; instead, it relies on another vehicle for movement.

Trailers typically serve the purpose of carrying goods, cargo, or equipment, making them essential in various aspects of transport and logistics. Their design allows them to attach securely to vehicles such as trucks, cars, or motorcycles, thereby facilitating the efficient transportation of materials from one location to another.

The other options describe different types of vehicles. One option pertains specifically to motor vehicles that transport passengers, which is not the function of a trailer. Another describes vehicles capable of independent movement, which pertains to self-propelled vehicles, while the choice that is similar to the correct option but lacks the specificity of being designed to be towed highlights a misunderstanding of the primary utility and characteristics of trailers.