Azolla has symbiotic relationship with which of the following?

Anabaena

The option 3 is correct . Azolla maintains a symbiotic relationship with Anabaena.

They work together and benefit each other. Azolla fern procures a safe environment for Cyanobacteria and in return, it gets nitrogen fixed by Anabaena. When Azolla dies, the nitrate fertilizer is released into the environment, where it becomes available to other plants.

Anabaena is a genus. It comprises of filamentous cyanobacteria that exist as plankton. They possess nitrogen-fixing abilities, and they form symbiotic relationships with certain plants, like the mosquito fern.