Who must a pilot present their certificate to upon request by authorities?

A pilot is required to present their certificate to the FAA (Federal Aviation Administration) or the National Transportation Safety Board (NTSB) upon request because these agencies are the governing bodies responsible for regulating and overseeing aviation safety in the United States. Authority figures from the FAA or NTSB are empowered to verify a pilot's credentials and ensure compliance with aviation regulations. This requirement plays a crucial role in maintaining aviation safety standards and ensuring that pilots are operating legally and competently.

The other options listed, while they may be relevant in different contexts, do not carry the same regulatory authority. For instance, a flight instructor may request to see a certificate for instructional purposes, but they do not have the legal responsibility to enforce regulations. Similarly, an airport manager or a fellow pilot may have an interest in a pilot's credentials, but they lack the formal authority to demand compliance in the same way that the FAA or NTSB does.