What should be noted regarding a health care proxy's role?

The role of a health care proxy is to make medical decisions on behalf of a client when they are unable to do so themselves, typically due to incapacitation or inability to communicate. This means that the proxy should act in the best interest of the client, based on the client's known wishes or, if those are not known, based on what the client would likely have wanted. The proxy's authority to make decisions comes into play specifically when the client is unable to express their preferences, making this option correct.

While it is important for the proxy to consider any advance directives or known values of the client, their primary function is to ensure that the client's health care preferences are respected, even if the client is not in a position to articulate them themselves. This highlights the essential responsibility and autonomy entrusted to the proxy in situations where the client cannot advocate for themselves.