What is the primary function of the tailgate on a pickup truck?

The primary function of the tailgate on a pickup truck is to open and allow cargo to be loaded into the bed. The tailgate acts as a barrier at the rear of the truck bed, enabling easy access for loading and unloading items. When the tailgate is down, it provides a larger opening, making it simpler to handle bulky items or large loads. This feature is essential for the practicality and utility of a pickup truck, as it enhances cargo management and overall convenience for the user.

The other options relate to different components or functions within a vehicle but are not relevant to the specific purpose of the tailgate. Supporting the windshield pertains to the vehicle's structural integrity, while connecting the chassis and the cabin refers to the overall framework of the vehicle. Protecting the rear axle involves aspects of the vehicle's drivetrain and suspension, which are not functions served by the tailgate. These options emphasize the diverse elements of vehicle design but do not align with the main role of the tailgate in facilitating cargo movement.