Which one of them is not a producer?

Volvox Nostoc Agaricus Spirogyra

Agaricus

Producers mainly include photosynthetic organisms that prepare their food with the help of sunlight and inorganic matter. Spirogyra, Volvox, and Nostoc are producers because they contain chlorophyll, which helps in photosynthesis. Agaricus belongs to species of saprophytic fungi, and it is also known as the mushroom. It does not contain chlorophyll. It undergoes saprotrophic mode of nutrition, to obtain n nutrition.