Which vehicle is eligible for coverage under the business auto coverage part?

The option that pertains to eligibility for coverage under the business auto coverage part is a private messenger auto. This is because the business auto coverage part is specifically designed to cover vehicles that are used in the course of conducting business activities. Since a private messenger auto is typically used for delivering documents or goods as part of a business operation, it falls squarely within the parameters of this type of coverage.

On the other hand, private passenger vehicles are usually covered under personal auto policies and may not provide the appropriate coverage for business use. A rental car used for business purposes could be covered under a different policy or endorsement, depending on the specifics of the business auto coverage and the terms provided. Lastly, while motorcycles can be used for delivery, they typically have separate coverage requirements and may not fall under the standard business auto coverage part. Therefore, the private messenger auto is the most aligned with the criteria set forth for business auto coverage.