Final answer:
A physician cannot refuse to treat a patient they already agreed to treat. They must always follow through with the prior agreement.
Step-by-step explanation:
A physician not being able to refuse treatment to a patient they have already agreed to treat means that they must always follow through with the prior agreement. Option D is the correct answer. Once a physician has agreed to treat a patient, they have a professional and ethical obligation to provide the necessary care to that patient.