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: Surgery
[{'content': 'Cardiac glycosides are obtained from following plant source: \nSelect and explain. \nA. Rauwolfia serpentina., B. Strophanthus gratus., C. Ricinus communis., D. Atropa belladonna.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The following are obtained from Rauwolfia serpentina--Reserpine. Strophanthus gratus--Strophanthin-G (Ouabain) A cardiac glycoside. Ricinus communis--Castor oil. Atropa belladonna--Atropine', 'role': 'assistant'}]