Cyanobacteria Are an Important Subgroup of Bacteria

Cyanobacteria are an important subgroup of Bacteria. Which of the statements about cyanobacteria is INCORRECT?

A) The ability of some cyanobacteria to fix nitrogen is used in rice cultivation.
B) Cyanobacteria may grow extensively in water and produce peptide toxins which are harmful to animals.
C) Early photosynthetic cyanobacteria are thought to be responsible for the earth's atmosphere becoming oxygen rich.
D) Stromatolites, which are formed by cyanobacteria are the oldest fossil evidence of life on earth.
E) Cyanobacteria contain chlorophyll and like other photosynthetic organisms, generate molecular oxygen during photosynthesis.