单选题 A client who suffered blunt chest trauma in a car accident complains of chest pain, which is exacerbated by deep inspiration. On auscultation, the nurse detects a pericardial friction rub--a classic sign of acute pericarditis. To relieve chest pain associated with pericarditis, the nurse should encourage the client to assume which position?
A. Semi-Fowler's.
B. Leaning forward while sitting.
C. Supine.
D. Prone.