Which of the following micro organisms are used as biofertilizer?

The correct answer is (a) Cyanobacteria.

Cyanobacteria are a type of bacteria that can produce oxygen through photosynthesis. They are often used as biofertilizers because they can fix nitrogen from the air, which is essential for plant growth. Cyanobacteria can also produce growth hormones and other compounds that promote plant growth.

Protozoa are a type of single-celled organism that can be found in soil and water. They are not used as biofertilizers because they do not fix nitrogen or produce other compounds that promote plant growth.

Viruses are not living organisms and cannot be used as biofertilizers.

Here is a more detailed explanation of each option:

• Cyanobacteria are a type of bacteria that can produce oxygen through photosynthesis. They are often used as biofertilizers because they can fix nitrogen from the air, which is essential for plant growth. Cyanobacteria can also produce growth hormones and other compounds that promote plant growth.
• Protozoa are a type of single-celled organism that can be found in soil and water. They are not used as biofertilizers because they do not fix nitrogen or produce other compounds that promote plant growth.
• Viruses are not living organisms and cannot be used as biofertilizers.