What should be done if there is slight arcing at the brushes and commutator?

When slight arcing occurs at the brushes and commutator, it can often be a normal occurrence in certain operating conditions and isn't necessarily indicative of a malfunction that requires immediate correction. Therefore, observing slight arcing does not always necessitate any action.

In many cases, minor arcing can result from normal wear or from the brushes not perfectly matching the commutator's surface. If the arcing is not excessive and does not lead to significant sparking, smoke, or brush wear, then maintenance might not be required.

However, it's important to monitor the situation to ensure it doesn’t escalate into a more serious issue, which could necessitate intervention. Hence, selecting 'None' suggests a sensible approach of active observation rather than immediate corrective action, especially if it hasn’t reached a level that would warrant concern.