The correct answer is option 4: 1, 2 and 3. Biofertilizers are organisms that contribute nutrients to plants in a natural and environmentally friendly way. The three types of organisms mentioned in the options - blue-green algae, ferns, and mosses - are commonly used as biofertilizers.
Blue-green algae, also known as cyanobacteria, are photosynthetic bacteria that can fix atmospheric nitrogen and convert it into a usable form for plants. They form a symbiotic relationship with some plants, providing them with nitrogen and enhancing their growth.
Ferns, on the other hand, are non-flowering plants that have a unique relationship with mycorrhizal fungi. These fungi help in nutrient absorption and improve the overall nutrient availability to the plants.
Mosses, although small in size, play an important role in nutrient cycling, particularly nitrogen. They can fix atmospheric nitrogen and contribute to the fertility of the soil.
Therefore, all three types of organisms mentioned in the options - blue-green algae, ferns, and mosses - are commonly used as biofertilizers because of their ability to contribute nutrients to plants and improve soil fertility.