In biological nitrogen fixation by microbes:
I. Rhizobium fixes nitrogen in the root nodules of leguminous plants
II. Frankia fixes nitrogen in the root nodules of non-leguminous [actinorrhizal] plants
III. Mycorrhiza are symbiotic relation between vascular plants and fungi [genus Glomus] that help plants absorb minerals like phosphorus
IV. Cyanobacteria [Anabaena, Nostoc and Oscillatoria] serve as important biofertlizers in paddy fields
1. Only I, II and III are correct
2. Only I, II and IV are correct
3. Only II, III and IV are correct
4. I, II, III and IV are correct