Final answer:
An adult client who cannot read is legally allowed to give informed consent.
Step-by-step explanation:
The client who is legally allowed to give informed consent in this scenario is an adult client who cannot read. Informed consent requires that the individual has the ability to understand the information being provided to them. While an unconscious client, a sedated client, and a 14-year-old with a broken arm may have legal representatives who can provide consent on their behalf, they are not capable of giving informed consent themselves.