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': 'Curdling of milk is caused by - \nSelect and explain. \nA. Rennin, B. Lipase, C. Amylase, D. Elastase', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is'a'i.e., Rennin [Ref: Concise oxford dictionary p. 1218iRennin is an enzyme secreted into the stomach of unweaned mammis causing the curdling of milk.", 'role': 'assistant'}]