A nurse is implementing a plan of care for a client who has a cough with sputum. The nurse suspects that the client has a respiratory infection. What is the nurse's priority?

A. Incorrect: Teaching about an incentive spirometer is important for lung expansion but is not the priority before confirming the infection. B. Incorrect: Monitoring the cough is essential but does not directly lead to a diagnosis. C. Correct: A sputum culture should be obtained before administering antibiotics to ensure appropriate treatment based on pathogen identification. D. Incorrect: Administering an antibiotic is important but should be done after obtaining a sputum culture to ensure proper selection of the antimicrobial agent.