Explanation:

- Let’s break it down: In an ecosystem, a pyramid of biomass shows the total mass of living things at each trophic level.

- Usually, in grassland ecosystems (Option 2 ), this pyramid is upright. That means producers (like grasses) have more biomass than herbivores, and herbivores have more than carnivores.

- In pond ecosystems (Option 1) and most freshwater ecosystems (Option 3), the pyramid of biomass can be inverted. Why? Because phytoplankton (producers) have less biomass at any one time than the animals grazing on them.

- Forest ecosystem (Option 4) can be upright, since trees (producers) form a massive biomass base. But because structure is complex, sometimes it’s less clear-cut.

- So, bottom line: In grassland ecosystems—yep, the pyramid’s upright, most biomass at the bottom, tapering up.