In order to support all of the organisms in an ecosystem, which should have the greatest amount of biomass? secondary consumers producers primary consumers decomposers

Answer is: producers.
Producers (autotrophs) make the food for the rest of this groups. Producers get energy from the sun and in reaction with water (photosynthesis) convert it into useable energy in the form of organic matter (sugar). For example plants and algaes are producers.

~potters6/te801/biology/biounits/respiration.htm

If the experiment was perfomed more then once and you get the same results