Which among the following is incorrect about Cyanobacteria?

• A. The word cyano means greenish-blue because of which cyanobacteria is also called as blue-green algae
• B. The colour of cyanobacteria is due to presence of chlorophyll
• C. Cyanobacteria are chemosynthetic autotrophs
• D. Cyanobacteria help in enriching oxygen levels in the atmosphere