This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
Primary action of superior oblique is- 
Select and explain. 
A. Intorsion, B. Depression, C. Adduction, D. Abduction
A: Intorsion
Answer: A: Intorsion 
Explanation: There are six extraocular muscles in each eye.