Final answer:
The correct response that shows understanding of advanced directives is the client's intent to appoint a healthcare proxy, a key aspect of living wills that empowers someone to make medical decisions on their behalf if needed.
Step-by-step explanation:
The client response that indicates an understanding of the teaching about advanced directives is "I should appoint a healthcare proxy in case I become unable to make decisions." This statement shows that the client comprehends the importance of designating a person to make medical decisions on their behalf if they are rendered incapable of doing so themselves. The concept of a healthcare proxy is a critical component of a living will or advance directive, ensuring that one's healthcare preferences are honored even when they cannot communicate their wishes.