This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuro-ophthalmology, Subject name: Ophthalmology
Longest pa of optic nerve - 
Select and explain. 
A. Intraocular, B. Intracranial, C. Intraorbital, D. Intracranial
C: Intraorbital
Answer: C: Intraorbital 
Explanation: The optic nerve is about 47- 50 mm in length and can be divided into 4 pas : intraocular (1mm), intraorbital (30mm), intracanalicular (6-9mm)and intracranial (10mm). Refer comprehensive ophthalmology 6th edition , A K Khurana , page no. 310