Final answer:
When faced with an unknown risk, a nurse should gather information and communicate with the client.
Step-by-step explanation:
When a client asks a nurse to perform an act that has an unknown risk, there are two important things the nurse should do. Firstly, the nurse should gather all the necessary information about the act and its potential risks. This may involve consulting medical literature, seeking advice from colleagues, or contacting the client's healthcare team. Secondly, the nurse should communicate with the client and ensure they are fully informed about the potential risks and benefits involved in the act. This includes explaining the uncertainties and helping the client make an informed decision.