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: Unknown
Length of intraorbital part of optic nerve is : 
Select and explain. 
A. 10-12 mm, B. 20-24 mm, C. 25-30 mm, D. 35-40 mm
C: 25-30 mm
Answer: C: 25-30 mm 
Explanation: Length of optic nerve – 5 cm

Intraocular portion – 20 mm
Intraorbital portion – 30 mm