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: Social & Preventive Medicine
The following statement about DDT is false: 
Select and explain. 
A. Pyrethrum has synergistic action, B. It is a contact poison, C. Immediately kills the prey, D. Residual effect lasts for 18 months
C: Immediately kills the prey
Answer: C: Immediately kills the prey 
Explanation: Immediately kills the prey Repeat from May 11 DDT does not immediately kill the insects. It takes several hours to kill them.