Which of the following provides instruction about life-sustaining medical treatment for a patient who has a terminal disease?

A health care proxy is a designated individual authorized to make medical decisions on behalf of a patient who is incapacitated. While it allows for the representation of the patient's wishes, it does not itself provide specific instructions about life-sustaining treatments; instead, it relies on the proxy’s understanding of the patient's desires.

Active euthanasia involves intentionally ending a person's life to relieve suffering, typically in cases of terminal illness. While it may relate to end-of-life choices, it does not provide instructions for life-sustaining treatment. Instead, it represents a decision to forego treatment entirely, which is distinctly different from a living will.

Organ donation refers to the process of giving one's organs for transplantation after death. Although it can be part of end-of-life planning, it does not provide any instructions related to life-sustaining medical treatments. It is a separate legal and ethical decision from the directives contained in a living will.