A motorcyclist wearing a full helmet was thrown from his motorcycle after hitting a patch of oil on the road. The bike had been traveling at a high rate of speed. Manual spine motion restriction is being maintained by an off-duty EMT. The primary assessment reveals the patient to be responsive to painful stimuli and breathing rapidly with slight sonorous airway sounds. His radial pulse is weak and fast. As you quickly scan his body, you note deformity to the left femur and lower leg. Your immediate action should be to:

A) Apply a cervical collar
B) Place a nonrebreather oxygen mask
C) Remove his helmet
D) Expose his left lower extremity

C) Remove his helmet