The correct answer is C. Benzene hexachloride.
Gammexane is a common name for the insecticide hexachlorocyclohexane (HCH), which is a mixture of isomers. The most common isomer is 1,2,3,4,5,6-hexachlorocyclohexane, also known as lindane.
Toluene is a colorless, flammable liquid that is used as a solvent and in the production of TNT.
Aniline is a colorless, flammable liquid that is used in the production of dyes and pharmaceuticals.
Chlorobenzene is a colorless, flammable liquid that is used as a solvent and in the production of pesticides.
Toluene, aniline, and chlorobenzene are all isomers of benzene, but they have different chemical properties. Benzene hexachloride is a mixture of isomers, but the most common isomer is lindane, which is a highly toxic insecticide.