4) Which of the following statements is/are correct?
A) In paddy fields, cyanobacteria serve as an important biofertiliser.
(B) Plants having mycorrhizal associations show functions like tolerance to drought, salinity and resistance to root-borne pathogens.
(C) The important examples of cyanobacteria as biofertilisers are Anabaena, Nostoc and Oscillatoria.
(D) All of these
