Step 1: Understanding the Concept
Gammexane (lindane) is the \(\gamma\)-isomer of hexachlorocyclohexane, an insecticide.
Step 2: Identify
Hexachlorocyclohexane is also known as benzene hexachloride (BHC), formed by adding \(\text{Cl}_2\) to benzene in sunlight.
Step 3: Compare the options
Benzene hexachloride is option (C). DDT is a different insecticide.
Final Answer:
Gammexane is benzene hexachloride.
\[ \boxed{\text{(C) }\text{Benzene hexachloride}} \]