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': 'Progesterone production in the ovary is primarily by: \nSelect and explain. \nA. Stroma, B. Corpora albicans, C. Corpora lutea, D. Mature follicles', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]