Final answer:
Under common law, a physician has a duty to treat a patient if there is a pre-existing doctor-patient relationship, regardless of convenience. However, this duty does not apply in emergency situations.
Step-by-step explanation:
Under common law, a physician has a duty to treat a patient under certain circumstances. The general rule is that a physician must treat a patient if there is a pre-existing doctor-patient relationship, regardless of the circumstances or convenience for the physician. This means that a physician cannot refuse to treat a patient just because it is inconvenient or because they did not have a prior agreement. However, this duty does not apply in emergency situations where there is an immediate threat to the patient's life or health.