For an individual ( not a repair station) to conduct a complete 100 hour inspection on an aircraft and approve it for return to service requires a mechanic certificate with:

For an individual ( not a repair station) to conduct a complete 100 hour inspection on an aircraft and approve it for return to service requires a mechanic certificate with and powerplant and airframe ratings

Explanation:

Because these are important certificates issued by the FAA giving the mechanic authority to inspect to inspect an aircraft and approve its return to services