Under what circumstance can a veterinarian discontinue treatment of a patient?

A veterinarian can discontinue treatment in scenarios where either the client requests to stop or when the treatment or diagnosis has been completed.

When a client expresses the desire to discontinue treatment, it is typically a reflection of their understanding of the patient's current condition and their treatment preferences. Veterinarians must respect the clients' decisions regarding their pet's care, provided it does not pose an immediate risk of harm to the animal, as long as the client is making an informed choice.

Additionally, once a treatment or diagnosis has been concluded, the veterinarian may appropriately cease further care for that specific issue, as their obligation ends when the necessary medical intervention has been provided and the case is resolved.

Both of these circumstances are legitimate and recognized within veterinary practice as valid reasons for a veterinarian to discontinue treatment, leading to the correct answer.