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
Toxic substance commonly used by washermen to put marks on clothes: Delhi 06 
Select and explain. 
A. Calotropis procera, B. Plumbago rosea, C. Semecarpus anacardium, D. Croton tiglium
C: Semecarpus anacardium
Answer: C: Semecarpus anacardium 
Explanation: Ans. Semecarpus anacardium