In an ecological pyramid, which trophic level is represented at the b…

The correct answer is Option (4) → Producers

An ecological pyramid shows the number, biomass or energy at each trophic level of a food chain, from the producers up to the top consumers. The level that holds the most comes at the broad base, and the levels above get narrower.

Option (1) Tertiary consumers — Incorrect. Tertiary consumers are the top level and form the apex of the pyramid.

Option (2) Secondary consumers — Incorrect. Secondary consumers form the third level, just below the apex.

Option (3) Primary consumers — Incorrect. Primary consumers (herbivores) form the second level, just above the base.

Option (4) Producers — Correct. Producers (green plants) form the first trophic level, so they make up the base. All other levels depend on them for food.

NCERT Extract:
Ecological Pyramids – “… The base of each pyramid represents the producers or the first trophic level while the apex represents tertiary or top level consumer. The three types of ecological pyramids that are usually studied are (a) pyramid of number; (b) pyramid of biomass and (c) pyramid of energy. For detail (see Figure 12.4 a, b, c and d).”

Figure 12.4 (a) Pyramid of numbers in a grassland ecosystem. Only three top-carnivores are supported in an ecosystem based on production of nearly 6 millions plants