Problem: A client is receiving oxygen by way of a nasal cannula at a rate of 2 L/minute and will be discharged with home oxygen. The nurse is reinforcing teaching with the client about setting the appropriate oxygen flow rate. What is the best statement for the nurse to make? "The top of the ball should sit on top of the line marked '2.'" "The bottom of the ball should sit on top of the line marked '2.'" "The line marked '2' should cut the ball in half." "Any part of the ball should touch the line marked '2.'"