A free living nitrogen fixing cyanobacterium which can also form symbiotic association with the water fern Azolla ………….. .

Options

A. Tolypothrix
B. Chlorella
C. Nostoc
D. Anabaena

Answer

D

Explanation

(d) Anabaena is a free living nitrogen fixing cyanobacterium which can form symbiotic association with water fern Azolla.