Final answer:
When a nurse hears profuse fine crackles in a patient's lungs, the next step is to ask the patient to cough and reauscultate the lungs to confirm the presence of crackles and assess any changes in their characteristics.
Step-by-step explanation:
When a nurse hears profuse fine crackles in a patient's lungs, it is important to take appropriate action. The next step for the nurse would be to ask the patient to cough and reauscultate the lungs (option d).
This is done to confirm the presence of crackles and assess any changes in their characteristics. Coughing can sometimes clear the airway and may result in the disappearance of crackles.