Final answer:
The fifth step in checking lung sounds is using a stethoscope to listen for breath sounds, a process known as auscultation.
Step-by-step explanation:
The fifth step to checking lung sounds in a patient is B. Use a stethoscope to listen for breath sounds. This method, known as auscultation, is critical for assessing the condition of a patient's lungs. By using a stethoscope, healthcare professionals can detect abnormal sounds such as crepitations, which might suggest the presence of conditions like pneumonia or other respiratory issues. Proper placement of the stethoscope on the chest allows for the accurate listening of these sounds.