Answer- C. Chest tube inseion and drainageThis case is a classical description of post RM traumutic pneumothorax of left hemithorax, with decreased breath sound and trachea shifted to the right. Presence of hea sounds indicstes absence of cardiac tamponade. Tension pneumothoro-r is ruled out, as the patient is not having hypotension (BP-120/80 mm Hg). So the first line management is chest tube inseion and drainage.