Which of the following describes the role of producers in an ecosyste…

The correct answer is Option (3) → They fix the Sun’s radiant energy to make food from simple inorganic materials.

Producers are autotrophs: green plants and photosynthetic bacteria. They fix the energy of sunlight to make food from simple inorganic materials, and every other organism depends on this food, directly or indirectly.

Option (1) They feed on herbivores and pass energy on to the top carnivores. — Incorrect. Feeding on herbivores is the role of carnivores (secondary consumers), not of producers.

Option (2) They degrade detritus into simpler inorganic substances. — Incorrect. Degrading detritus into simpler inorganic substances is the work of the decomposers, mainly bacteria and fungi.

Option (3) They fix the Sun’s radiant energy to make food from simple inorganic materials. — Correct. Producers fix the Sun’s radiant energy and make food from simple inorganic materials. This is the input of energy for the whole ecosystem.

Option (4) They occupy the apex of the pyramid of energy. — Incorrect. Producers form the base of every ecological pyramid. The apex is occupied by the tertiary or top-level consumers.

NCERT Extract:
Energy Flow – “… Of the incident solar radiation less than 50 per cent of it is photosynthetically active radiation (PAR). We know that plants and photosynthetic bacteria (autotrophs), fix Sun’s radiant energy to make food from simple inorganic materials. Plants capture only 2-10 per cent of the PAR and this small amount of energy sustains the entire living world.”
Ecological Pyramids – “… The base of each pyramid represents the producers or the first trophic level while the apex represents tertiary or top level consumer.”