Which were the first organisms to release oxygen by photosynthesis?

A) Algae
B) Cyanobacteria
C) Gymnosperms
D) Flowering plants
E) Green sulfur bacteria

Cyanobacteria

Photosynthetic microorganisms, also known as blue-green algae, that are important for oxygen production and are found in many aquatic environments.

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.

Algae

Algae is a broad and diverse group of photosynthetic, usually aquatic, organisms that range from single-celled forms to large seaweeds.