In which of the following Azolla symbiotically associates to fix atmospheric nitrogen

Correct option is A

Cyanobacteria = Bacteria (NOT Algae)
So, the correct classification is: (a) Bacteria

• Anabaena azollae (which lives in Azolla) is a cyanobacterium.
• Though commonly called "blue-green algae," it is not a true algae but a photosynthetic bacterium.
• Modern biology places cyanobacteria in the domain Bacteria
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• Azolla forms a symbiotic relationship with cyanobacteria (Anabaena azollae), which are bacteria.
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• So the most scientifically accurate answer would be (a) Bacteria, even though many books still list "algae" due to historical classification.
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• , not Protista (where true algae belong).