Which of the following is true about a living will?

A living will is a legal document that allows individuals to express their preferences regarding medical treatment in the event that they become unable to communicate their wishes due to illness or incapacity. This document specifically outlines the types of medical interventions a person wants or does not want, such as life-sustaining treatments, resuscitation, and palliative care.

The significance of this option lies in the fact that it ensures that healthcare providers and family members are aware of the individual's desires, thereby guiding medical decisions when the person is no longer able to advocate for themselves. This clarity helps to reduce confusion and potential conflicts often arising during critical medical situations, ensuring that the person's autonomy and wishes are respected.

The other options do not correctly reflect the nature of living wills. While living wills may have varying recognition across different states, stating that they are valid only in certain states doesn't represent the overarching principle of their existence. Furthermore, a living will does not override all health care decisions; it specifically pertains to the individual's expressed wishes and must be considered along with other legal documents, such as durable power of attorney for health care. Lastly, changes to a living will typically must be made in writing rather than verbally, ensuring that updates are documented formally.