The correct option is C Cycas
Cyanobacteria, which have "symbiotic" relationships with cycads are in the order Nostocales. Anabaena cycadeae is a blue green algae (BGA) commonly found in the coralloid roots of cycads. At first, the cycad sprouts without any cyanobacterium. Coralloid roots are formed soon after the primary root.
So answer is - 'Cycas'.