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: Physiology
[{'content': 'Hot water bottle relieves the pain of abdominal spasm by \nSelect and explain. \nA. Stimulation of adrenergic fibers, B. Stimulation of cholinergic fibers, C. Inhibition of cold receptors, D. Inhibition of heat receptors', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Pain from gastrointestinal viscera is carried by small C fibers. Temperature sensation from hot water bottles passes through A fibers and large C fibers. \nWhen these larger fibers are stimulated, they block the adrenergic small C fibers from the viscera.', 'role': 'assistant'}]