Final answer:
The clear indication that the client understands how to use a peak flow meter is if they say they will base the score on the best of three attempts.
Step-by-step explanation:
The correct statement that indicates the client understands how to use a peak flow meter is: "I will base my peak flow meter score on the best of three attempts." This technique ensures that the measurement is accurate and not affected by a poor effort or a mistake during the process. Blowing out as hard as one can before using the device does not relate to the correct use of a peak flow meter and should not be done before taking a reading. Taking controller medication is still necessary even if peak flow scores are in the so-called yellow zone; this indicates that there is some obstruction, but action can be taken to prevent further asthma deterioration. Lastly, the green zone on a peak flow meter indicates good asthma control, and a visit to the emergency room would typically not be necessary unless other symptoms warrant it.