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: Anatomy
[{'content': 'True statement about upper half anal canal is: \nSelect and explain. \nA. Insensitive to pain, B. Drained by superficial inguinal lymph node, C. Lined by squamous epithelium, D. Supplied by superior mesentric aery', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Insensitive to pain', 'role': 'assistant'}]