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
[{'content': 'Not a part of medial wall of orbit \nSelect and explain. \nA. Frontal bone, B. Ethmoid bone, C. Lesser wing of sphenoid, D. Tip of maxilla', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]