state gov WBPSC Miscellaneous Services Mock Test 2023 General Knowledge Ecology and Environment Ecology and Functions of an ecosystem
Consider the following organisms:
1. Rhizobium
2. Nostoc
3. Azolla
4. Cyanobacteria
Which of the above-given organisms can be used as bio-fertilisers?
1
1 only
2
2 and 3 only
3
1, 3 and 4 only
4
1, 2, 3 and 4