The correct option is C Blue-green algae
Cyanobacteria
are also referred as blue-green algae. They are members of monera. They are called
blue-green algae because they are aquatic and photosynthetic. They are Gram
positive photosynthetic prokaryotes which perform oxygenic photosynthesis. They
are one of the most successful autotrophic organisms on earth which have
mastered all types of environments- fresh water, sea water, salt marshes, moist
rocks, tree trunks, moist soils, hot springs, frozen waters. Blue-green algae
may be unicellular, colonial or filamentous. Cells are larger and more
elaborate than bacteria. Heterocyst is present for nitrogen fixation.