Which feature of some species of blue green algae helps promote them as bio-fertilisers ?

• A. They convert atmospheric methane into ammonia which the crop plants can absorb readily
• B. They induce the crop plants to produce the enzymes which help convert atmospheric nitrogen to nitrates.
• C. They have the mechanism to convert atmospheric nitrogen into a form that the crop plants can absorb readily
• D. They induce the roots of the crop plants to absorb the soil nitrates in larger quantities.