This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
The following are small residual insecticides EXCEPT - 
Select and explain. 
A. Pyrethrum, B. DDT, C. Gamma BHC, D. Malathion
A: Pyrethrum
Answer: A: Pyrethrum 
Explanation: Anti-adult measures: Residual sprays (DDT, Lindane, Malathion, OMS-33) Space sprays (Pyrethrum extract, residual space insecticide - Malathion and fenitrothion fogging) Park's Textbook of Preventive and Social Medicine, 25th Edition, Pg 833