Cyanobacteria pumped this into the atmosphere, creating an ozone layer. nitrogen oxygen methane ammonia

The correct answer is option (B) oxygen.

Cyanobacteria are the only prokaryotic organisms which obtain energy from the process of photosythesis. It is the process of forming organic compounds using energy from the sun, water, carbon dioxide and chlorophyll releasing oxygen abundantly into the atmosphere. Ozone is formed when the ultraviolet radiations react with the oxygen molecules in the atmosphere, splitting them into individual atoms of oxygen. These atoms of oxygen react with the oxygen molecules released during photosynthesis to form ozone (). Thus, Cyanobacteria pump up oxygen into the atmosphere, creating an ozone layer.