The early atmosphere
a. was essentially the same as occurs now.
b. was changed drastically by the liberation of oxygen following the evolution of photosynthesis.
c. was characterized by high concentrations of oxygen and ozone.
d. was characterized by high concentrations of inert gases before the evolution of living organisms.
e. was so dense that life could not evolve.
Answer: b. was changed drastically by the liberation of oxygen following the evolution of photosynthesis.
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