In which part of regulations can suspension or revocation grounds be found?

The correct choice is related to the regulations governing aviation, specifically those concerning the certification and responsibilities of pilots. Part 61 outlines the certification requirements for pilots, mechanics, and other personnel involved in aviation. Within this part, you will find the rules that establish the basis for the issuance of pilot certificates, including the conditions under which these certificates can be suspended or revoked.

This includes grounds such as violation of regulations, medical disqualifications, or other safety-related issues that could affect a pilot's ability to operate an aircraft safely. Understanding Part 61 is crucial for anyone involved in operating aircraft, as it ensures compliance with necessary regulations to maintain safety in the aviation environment.

The other options pertain to different aspects of aviation regulations. Part 45 deals with identification requirements for aircraft, Part 91 addresses general operating and flight rules, and Part 107 specifically outlines regulations for small unmanned aircraft systems (drones). Each of these has its own focus and does not cover the suspension or revocation of pilot certifications, which is why they do not align with the question's requirement.