Which form acts as proof that the provided vehicle meets requirements to transport ammunition?

DD Form 626 is the correct choice because it serves as a certification that a vehicle is inspected and meets all necessary requirements for transporting ammunition. The form ensures compliance with safety and security standards established for the handling and movement of hazardous materials, specifically ammunition. It includes information about the vehicle and the results of the inspection, such as the condition of the vehicle and necessary safety features. This documentation is crucial for maintaining safety protocols and ensuring that personnel and the environment are protected during the transportation of potentially dangerous materials.

The other forms mentioned have different purposes: DA Form 5811 is related to the accountability of ammunition and explosives, DA Form 7708 is used for operational readiness inspection notes, and Standard Form 91 pertains to vehicle accident reports. None of these forms provide the specific certification needed for vehicle compliance in the context of transporting ammunition.