参考答案：C

解析：

General anesthesia and postoperative pain may lead to immobility, which predisposes to respiratory complications postoperatively. Changing positions, along with coughing and deep breathing, is done to prevent respiratory complications. It’s unlikely that an otherwise healthy young woman would develop pressure ulcers during a brief postoperative period. Muscular stiffness would, of course, be decreased with frequent turning, but this isn’t the most important rationale for turning. Turning may decrease venous stasis, but a more effective intervention to decrease venous stasis in the early postoperative period would be leg exercises.