Which of the following is NOT a function of the tailgate on a pickup truck?

The tailgate of a pickup truck primarily serves multiple practical functions, but protecting passengers is not one of its primary roles. The main purpose of the tailgate includes facilitating cargo loading by providing a barrier to the cargo area, which allows for easier access when loading and unloading items. It also serves to provide structural support to the bed of the truck when in place, reinforcing the overall integrity of the vehicle's cargo area.

While the tailgate can contribute indirectly to vehicle safety by securing loads and preventing cargo from falling out during transport, it does not have a direct function related to passenger protection. The design and safety features regarding the protection of passengers are typically handled by the vehicle's cabin structure, seat belts, airbags, and various safety systems.