This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Techniques of Ocular Examination and Diagnostic Tests, Subject name: Ophthalmology
[{'content': 'Axial length of orbit: \nSelect and explain. \nA. 2.5 mm, B. 2.5 cm, C. 2 mm, D. 2 cm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) 2.5 cmRef.: A.K. Khurana 6th ed. / 3* Axial length of orbit is 24 mm i.e. 2.4 cm* Volume of orbit: 6 ml* Depth of anterior chamber: 3 mm* Eyeball Made of 3 layers:# Sclera: Outer# Choroid: Middle (vascular layer; a dangerous layer)# Retina: Inner* Cornea forms anterior l/6th of eyeball and sclera forms posterior 5/6th of eyeball', 'role': 'assistant'}]