Your interviewer fully understands that Registered Nurses are often the go-to for questions from patients and their families. They also know it's impossible for even the best and most experienced RN to know the answers to every question that comes their way. What they are looking to hear is that you can be resourceful in finding a solution. As you answer, talk about your willingness to tap into physicians, colleagues, policies, or any other materials to best help answer questions that may come your way. If you have an example of a time where you had to be creative in your resourcefulness to answer a question, don't hesitate to talk about it.