The detritus food chain (DFC) begins with:

The correct answer is Option (3) → Dead Organic matter

Option (1) Green plants — Incorrect. Green plants (producers) begin the grazing food chain (GFC), such as grass → goat → man.

Option (2) Carnivore — Incorrect. Carnivores feed on other animals and stand at the upper levels of a food chain, never at its start.

Option (3) Dead Organic matter — Correct. The detritus food chain starts with detritus: dead leaves, dead animals and wastes. Decomposers such as fungi and bacteria feed on it.

Option (4) Herbivore — Incorrect. Herbivores are the primary consumers of the grazing food chain, its second link.

NCERT Extract:
Energy Flow – “The detritus food chain (DFC) begins with dead organic matter. It is made up of decomposers which are heterotrophic organisms, mainly fungi and bacteria. They meet their energy and nutrient requirements by degrading dead organic matter or detritus. These are also known as saprotrophs (sapro: to decompose).”