Biomass is the total mass of organisms at a trophic level.
An organism is a living thing.
Biomass is the total mass of living things at a trophic level.
Biomass is the total mass of what at a trophic level?

(1) Plants growth
(2) peachleaf willow
(3) Conifers
(4) animals
(5) living things
(6) Most plants
(7) all matter
(8) insects