In which ecosystem is the biomass of primary consumers greater than p…

The correct answer is Option (4) → Sea

Option (1) Forests — Incorrect. The trees of a forest have far more biomass than the herbivores feeding on them, so the pyramid of biomass is upright. A single big tree can carry many insects, but that inverts only the pyramid of numbers.

Option (2) Grassland — Incorrect. The grasses outweigh the grazing animals, so the pyramid of biomass is upright.

Option (3) Desert — Incorrect. Desert plants are few, but the consumers are fewer still. Producers still have more biomass than herbivores, and the pyramid is upright.

Option (4) Sea — Correct. Phytoplankton are tiny and short-lived but multiply very fast. So at any one time the standing biomass of the fishes is larger, and the pyramid of biomass is inverted.

NCERT Extract:
Ecological Pyramids – “… In most ecosystems, all the pyramids, of number, of energy and biomass are upright, i.e., producers are more in number and biomass than the herbivores, and herbivores are more in number and biomass than the carnivores. Also energy at a lower trophic level is always more than at a higher level. There are exceptions to this generalisation: … The pyramid of biomass in sea is generally inverted because the biomass of fishes far exceeds that of phytoplankton.”