Answer:
The correct statements would be
Cyanobacteria, also termed as blue-green algae are the prokaryotes which are able to perform photosynthesis.
They were the major contributors of oxygen in the atmosphere and thus helped the organisms that rely on oxygen to evolve.
By the process of endosymbiosis, they lead to the origin of plants. The chloroplasts present in green plants is considered as the cyanobacteria living in the plant cell. It helps in photosynthesis and in return plants cell provides shelter to it.
It is believed that the oxygen released from early cyanobacteria reacted with dissolved iron ions to form iron oxide.