Which type of vehicle is not primarily designed for cargo?

The correct choice is the dune buggy because it is primarily designed for recreational use rather than for transporting cargo. Dune buggies are typically lightweight, open-bodied vehicles equipped for off-road driving in sandy or rugged terrains. They are built for performance and enjoyment, often featuring unique styling and insufficient space for carrying significant loads.

In contrast, trucks and truck tractors are designed specifically for the transportation of goods. Trucks are meant for hauling various types of cargo, while truck tractors serve as the front section of a transport vehicle designed to pull trailers that carry even larger loads. Trailers, as well, are structures specifically built to hold cargo, which further emphasizes that they are intended for cargo transport. Hence, the dune buggy stands out as the type of vehicle not primarily meant for cargo.