Consider the following organisms: 1. Agaricus 2. Nostoc 3. Spirogyra Which of the above is/are used as biofertilizer/biofertilizers?

Out of the three organisms listed, only 2. Nostoc is commonly used as a biofertilizer.

Agaricus: This is a type of mushroom and not typically used as a biofertilizer.

Nostoc: This is a filamentous, nitrogen-fixing cyanobacterium. Cyanobacteria, also known as blue-green algae, are one of the main groups of organisms used in biofertilizers due to their ability to fix atmospheric nitrogen and make it available to plants.

Spirogyra: This is a green alga and not generally used as a biofertilizer.