Billions of years ago, the atmosphere on the Earth did not have free oxygen. Scientists call it highly (blank) atmosphere.
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Answers
Answer:
Scientists believe that the Earth was formed about 4.5 billion years ago. Its early atmosphere was probably formed from the gases given out by volcanoes. ... The early atmosphere was probably mostly carbon dioxide, with little or no oxygen. There were smaller proportions of water vapour, ammonia and methane.
Explanation:
Earth's early atmosphere and oceans were devoid of free oxygen, even though tiny cyanobacteria were producing the gas as a byproduct of photosynthesis. ... This period, known as the Great Oxidation Event, changed chemical reactions on the surface of the Earth completely
Answer:
Highly reducing atmosphere.
Explanation:
If its for plato It says the answers on the tutorials, this one was on Ocean Habitats. I recommend doing the tutorials first then taking the pretest its alot less work in the long run unless you find the answers here of course :)