an 18-year-old college freshman presents to the emergency room for evaluation of fever, headache, and neck stiffness. on physical examination, the patient is resting quietly and has a flushed face. his vital signs are as follows: temperature, 104 f; pulse, 110 bpm; and bp, 105/70 mm hg. he has no rashes. during the physical examination, you flex the patient's neck and his hips and knees flex in response, indicating meningeal irritation. the name of this positive sign is: