A 21-year-old Caucasian male is brought to the emergency room by his girlfriend on his birthday. She says he has been complaining of a headache and dizziness and she is concerned about the amount of...

A 21-year-old Caucasian male is brought to the emergency room by his girlfriend on his birthday. She says he has been complaining of a headache and dizziness and she is concerned about the amount of alcohol he drank. His physical exam is notable for slurred speech and a rapid, repetitive, rhythmic horizontal beating motion of both eyes when he gazes to the right or left. What is this  motion called?

 A. Nystagmus

 B. Amblyopia

 C. Diplopia

 D. Strabismus