The correct answer is D) inspect for wear and misalignment of main contacts. When performing maintenance on circuit breaker contacts, the primary focus should be on inspecting the contacts for any signs of wear or misalignment. This is in line with the regulations and best practices for maintaining the safety and reliability of electrical systems. Applying a film of oil or using abrasive materials to dress the contacts could potentially compromise the integrity of the connection and introduce contaminants, which is not recommended. Smoothing roughened contact surfaces with a file may address some issues, but it does not address the underlying causes of wear or misalignment.