Final answer:
The medical assistant should inform the physician and seek guidance when a caller refuses to identify themselves but wants to talk to the physician.
Step-by-step explanation:
If a caller to a medical office wants to talk to a physician but refuses to identify themselves, the appropriate action for a medical assistant to take would typically be to inform the physician and ask for guidance (Option C). This ensures that the physician is aware of the situation and can make an informed decision on how to proceed, while also maintaining patient confidentiality and security protocols. It is important for medical assistants to adhere to office policies and the physician's preferences in these situations.