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: Forensic Medicine
[{'content': 'Toxic substance commonly used by washermen to put marks on clothes: Delhi 06 \nSelect and explain. \nA. Calotropis procera, B. Plumbago rosea, C. Semecarpus anacardium, D. Croton tiglium', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Semecarpus anacardium', 'role': 'assistant'}]