Which of the following constitutes the first trophic level?

The correct answer is Option (1) → Plants

Option (1) Plants — Correct. They make food by photosynthesis, so all other organisms depend on them.

Option (2) Herbivores — Incorrect. Herbivores, like the caterpillar in the figure, are primary consumers: the second trophic level.

Option (3) Carnivores — Incorrect. Carnivores that eat herbivores, like the sparrow, form the third trophic level.

Option (4) Omnivores — Incorrect. Omnivores eat both plants and animals, so they feed at the second level or higher, never the first.

NCERT Extract:
Energy Flow – “… Organisms occupy a place in the natural surroundings or in a community according to their feeding relationship with other organisms. Based on the source of their nutrition or food, organisms occupy a specific place in the food chain that is known as their trophic level. Producers belong to the first trophic level, herbivores (primary consumer) to the second and carnivores (secondary consumer) to the third (Figure 12.2).”
Population Interactions – “… You can think of predation as nature’s way of transferring to higher trophic levels the energy fixed by plants.”