Which vehicle is described as a trailer?

The correct answer describes a trailer as a vehicle designed specifically to carry loads without having its own propulsion system. A trailer is typically towed by a motorized vehicle, which provides the necessary power for movement. This definition aligns with the common understanding of what a trailer is in transportation terms.

While other choices describe vehicles with specific characteristics, they do not meet the primary criteria for what constitutes a trailer. For instance, vehicles that carry loads using their own power are self-propelled and do not fit the definition of a trailer. Similarly, a description emphasizing a non-motorized vehicle for temporary activity may apply to certain types of equipment or tools but does not encapsulate the nature of a trailer as used within transportation contexts. Therefore, the emphasis on the design of the vehicle to carry loads wholly on its own structure aligns perfectly with the true nature of a trailer.