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: Medicine
[{'content': 'A child presents with unilateral proptosis which is compressible and increases on bending forwards. It is non-pulsatile and has no thrill or bruit. MRI shows retroorbital mass with echogenic shadows. The most probable diagnosis is \nSelect and explain. \nA. Orbital varix, B. Orbital encephalocoele, C. Orbital A-V malformation, D. Neurofibromatosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]