To qualify for an Air Force tank cleaning contract, a contractor must provide proof of completing similar work on how many projects?

To qualify for an Air Force tank cleaning contract, a contractor must demonstrate experience through the successful completion of a specific number of similar projects. In this case, the requirement is to provide proof of having completed three such projects. This number is significant as it illustrates the contractor's capability and reliability in handling the specialized task of tank cleaning, which requires specific skills, knowledge, and adherence to safety standards.

Having completed three projects not only showcases the contractor's experience but also helps assure the Air Force that they have been adequately tested in various scenarios associated with tank cleaning. This level of experience reduces the risk of issues arising during the actual contract period, thus enhancing operational efficiency and safety.

The other options represent lower thresholds of project completion, which do not fully satisfy the requirement for the level of experience expected by the Air Force for such a specialized task.