Biomass pyramids decrease up trophic levels

Steps:

• Producers form the base with 800 g/m² biomass.
• Herbivores consume producers, typically 10% energy transfer, so their biomass is about 10% of producers: 80 g/m².
• Carnivores eat herbivores, again ~10% transfer, so ~10% of herbivores: 8 g/m².
• Closest values are herbivores 40 g/m² (half of expected, but fits pattern) and carnivores 4 g/m² (half again).

Why A is correct:

• Matches the pyramid rule where biomass halves or reduces by ~90% per level from producers (800) to herbivores (40) to carnivores (4).

Why the others are wrong:

• B: Equal carnivore and herbivore biomass violates decreasing pyramid.
• C: Herbivores (400) exceed producers (800) by half, impossible in pyramid.
• D: Carnivores (400) vastly exceed herbivores (40), inverting the pyramid.

Final answer: A