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The aquatic fern, which is an excellent biofertiliser is
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- Azolla
- Salvinia
- Marsilia
- Pteridium
Correct Option: A
Azolla is a freshwater fern harbouring a bluegreen alga - Anabaena in its leaf cavities. The alga fixes atmospheric nitrogen and releases nitrogenous compounds in leaf cavities. This symbiotic system is the main source of algal biofertilizer in rice fields.