Biofertillzer is
1. farmyard manure consisting of a mixture of cattle dung and crop residue
2. green manure in which quick growing crop is cultivated and ploughed under the soil
3. a cyanobacteria like Anabaena species living in the cavities of Azolla species
4. symbiotic bacteria like Azotobacter which fix atmospheric nitrogen

Options

A. farm yard manure consisting of a mix- ture of cattle dung and crop residue
B. green manure in which quick growing crop is cultivated and plaughed unde the soil
C. a cyanobacteria like Anabaena spe?ies living in the cavities of Azolla species
D. symbiotic bacteria lik.e Azotobacter which fix atmospheric nitrogen

Answer

3