Question

in the energy pyramid, the greatest biomass appears at the level of
a birds and mammals.
b insects and zooplankton.
c phytoplankton
d small fish and other aquatic species

Explanation:

In an energy pyramid, biomass (total living matter) decreases as you move up trophic levels because only ~10% of energy transfers between levels. Phytoplankton are producers (base of the pyramid), supporting all higher levels, so they have the greatest biomass.

Answer:

C. Phytoplankton