The answer obviously is A.
<u>Answer:</u>
Scientist think colonies of Cyanobacteria called stromatolites were responsible for the introduction of oxygen into earths atmosphere is true.
<u>Explanation:</u>
- In primeval earth’s atmosphere, stromatolites (colonies of Cyanobacteria) are believed to have increased the level of oxygen by their photosynthesis process.
- These are the first known organisms that started photosynthesis process and produced the oxygen to the earth’s atmosphere.
- There is a theory that, these organisms produced oxygen in the environment and the organism disappeared that couldn’t live in the atmosphere with the oxygen.
- Scientists gave this a name called as “great oxygenation event”.
D - Archaea
All organisms are unicellular & they live in extreme environments, like heat and salt.
4-)The first flowering plants were introduced toward the end of the Mesozoic era.
