Explanation:

Ecological pyramids illustrate the trophic structure of an ecosystem. A pyramid is considered 'inverted' when the biomass or number of organisms at a lower trophic level is less than that at a higher trophic level. Option (4) 'Pyramid of Biomass in Pond ecosystem' is typically inverted. This is because the producers (phytoplankton) have a very short lifespan and reproduce rapidly, so their standing crop biomass at any given time is small, but they support a larger biomass of primary consumers (zooplankton) and secondary consumers (fish). Option (1) 'Pyramid of Numbers in a grassland' is generally upright. Option (2) 'Pyramid of Energy in Pond ecosystem' (or any ecosystem) is always upright because energy transfer is inefficient, with significant loss at each trophic level. Option (3) 'Pyramid of Biomass in a grassland' is generally upright, with a large biomass of producers (grass) supporting smaller biomasses of consumers.