What are the two primary parts of a paver?

The two primary parts of a paver are indeed the tractor unit and the screed unit. The tractor unit is responsible for the movement of the machine and provides the necessary traction and propulsion needed to navigate the construction site. It typically includes the engine and drive components.

The screed unit is the component that actually lays the material, such as asphalt or concrete, into place. It levels and finishes the material to the desired thickness and smoothness, ensuring the final surface meets specifications. The combination of these two units allows the paver to perform its primary function of efficiently placing material while maintaining consistent quality in the finished roadway.

The other options mention components that, while relevant in other contexts, do not accurately capture the primary functional parts of a paver as set by industry standards.