Which type of vehicle is primarily designed for drawing other vehicles?

The most accurate choice is a truck-tractor, as this type of vehicle is specifically designed to pull other vehicles, particularly semi-trailers. Truck-tractors feature powerful engines and a configuration that enables them to provide the necessary torque and power to tow significant loads. Their design includes a fifth wheel coupling that allows for easy connection and disconnection from the trailers they haul, making them the primary choice for transporting freight over long distances.

In contrast, a semi-trailer refers to the type of trailer that is designed to be coupled with a truck-tractor for hauling goods but is not capable of being driven independently on its own. A passenger vehicle is optimized for personal transportation and is not designed to tow other vehicles. A commercial vehicle encompasses a broader category that includes various types of vehicles used for business purposes, such as trucks and vans, but does not specifically refer to those designed for drawing other vehicles. Thus, the truck-tractor clearly stands out as the correct answer for its designated purpose.