A 39 year old woman has diplopia several times a day for 6 weeks, she consults a physician when the double vision becomes unremitting, and also complains of dull pain behind her right eye. The cranial nerve injury likely to be responsible for all of these observations is one involving

a. d-The Sixth CN
b. a-The second cranial nerve
c. e-all of them
d. c-The fourth CN
e. b-The third CN