A 26-year-old woman with multiple sclerosis comes to the physician because of a recent relapse Examination of the eye movements shows slow adduction of the left eye with an associated right-beating nystagmus in the right eye. 

Which of the following is the location of the pathology that underlies this abnormality?: (A) Abducens nerve palsy, (B) Left medial longitudinal fasciculus, (C) Right medial longitudinal fasciculus, (D) Right oculomotor nerve
Answer is B. None