To whom must a conductor furnish his badge number?

The conductor is required to furnish his badge number to anyone who asks for it because this practice upholds transparency and accountability. Providing a badge number allows individuals to identify the conductor and helps ensure that they are operating under the authority and regulations tied to that particular role. This openness fosters trust between the conductor and the public as passengers can verify the identity of the staff member assisting them.

In this context, the conductor's badge number serves as a form of identification related to their official duties and responsibilities. It can also be crucial for reporting incidents, addressing concerns, or receiving feedback regarding performance and passenger interactions.

Other choices suggest limitations on who can ask for the badge number, which does not align with the principle of accessibility and accountability in a service-oriented environment. The badge number should be readily available to all, especially to passengers who may need to raise concerns or provide feedback about their experience.