The correct option is A Primary producers is larger than primary consumers.
The bottom of the biomass pyramid represents the primary producers (autotrophs). The primary producers trap energy from the sunlight or inorganic chemicals and use it to create energy-rich molecules such as carbohydrates. This mechanism is called as primary production. When energy is transferred from one trophic level to the next, typically only ten percent is used to build new biomass. The remaining ninety percent goes to metabolic processes or is dissipated as heat. The primary consumers are arranged above the producers as because they are less in number. Hence, the correct answer is option A.