You are transporting a patient who experienced a right-sided head injury after a large refrigerator fell and pinned his head between the appliance and the floor. On scene, the patient was responsive to verbal stimuli with the following vital signs: pulse, 96 beats/min; respirations, 16 breaths/min; blood pressure, 134/66 mmHg; and SpO2, 95%. During transport, as you reassess the patient, what would be the clearest sign that the head injury is worsening?

A) Increasing edema to the right side of the head
B) Blood pressure of 108/68 mmHg
C) Responding only to painful stimuli
D) Heart rate of 112 beats/min

C) Responding only to painful stimuli