Final answer:
The ethical principle of autonomy is best supported by explaining the benefits and risks of a medical procedure to a patient or their proxy, and by respecting a patient's decision to accept or refuse medical interventions.
Step-by-step explanation:
The principle of autonomy is one of the fundamental ethical principles in health care, which emphasizes the patient's right to make informed decisions about their own medical treatment. In the context of the given options, autonomy is best supported when B. Explaining the benefits and risks of enteral nutrition to the wife of a man in a persistent vegetative state and D. A patient at end of life is allowed to refuse parenteral nutrition. Both scenarios involve providing necessary information or respecting a patient's decision, which are key aspects of upholding this principle. While treating patients with similar attention and providing necessary nutritional support fall under the principle of beneficence, they do not specifically address autonomy which is central to a patient's self-determination and informed consent.