This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ocular motility and squint, Subject name: Ophthalmology
The muscle which makes an angle of about 51deg with the optical axis is 
Select and explain. 
A. Superior oblique, B. Superior rectus, C. Inferior rectus, D. Lateral rectus
A: Superior oblique
Answer: A: Superior oblique 
Explanation: The extraocular muscles rotate the eyeball around veical, horizontal and antero-posterior axes. Medial and lateral rectus muscles are almost parallel to the optical axis of the eyeball; so they have got only the main action. While superior and inferior rectus muscles make an angle of 23deg and reflected tendons of the superior and inferior oblique muscles of 51degwith the optical axis in the primary position. Ref:- A K KHURANA; pg num:-315