Which of the following is an insecticide?

Answer: (b) DDT

DDT (dichlorodiphenyltrichloroethane) is an organochlorine insecticide.

The idea

DDT belongs to the organochlorine family. It was the first modern synthetic insecticide, and was used in the Second World War against lice (typhus) and mosquitoes (malaria).

TNT → explosive → DDT → insecticide → Salicylic acid → medicine (aspirin is made from it) → Ammonium phosphate → fertiliser

Why the others are wrong

(a) TNT (trinitrotoluene) is an explosive.

(c) Salicylic acid is used in acne creams and to make aspirin.

(d) Ammonium phosphate is a fertiliser.

The trap

TNT and DDT look alike as three-letter chemicals.

Also know

Insecticides also come from plants: azadirachtin from neem and pyrethrum from chrysanthemum flowers. Bt is a soil bacterium whose protein kills caterpillars; its gene is used in Bt cotton.