A 25-year-old bull rider developed neck pain and vertigo after landing head first when he was thrown from a bull. Physical examination in the emergency department revealed that the man had decreased pain and temperature sense on the left half of his face and right side of his body, a Horner's syndrome on the left, and hoarseness and unsteady gate. An occlusion in which of the following vessels would most likely explain the deficits experienced by this patient?
A) Posterior inferior cerebellar artery B) Anterior inferior cerebellar artery C) Basilar artery D) Vertebral artery E) Anterior spinal artery