Which of the following accurately reflects the beliefs on earth's early history?
a. scientists believe that microspheres nearly prevented the development of early life.
b. scientists believe that dna may have existed before rna.
c. scientists believe oxygen was plentiful in the early atmosphere.
d. scientists believe the early atmosphere lacked the oxygen necessary to support modern human life.

d. Scientists believe the early atmosphere lacked the oxygen necessary to support modern human life. 

There are a lot of created theories in which biologists engaged themselves to explain such phenomenon that occurred thousands of years ago, and experts say such study is hard to replicate, the start of prokaryote cells. Prokaryotes were said to be the first organisms that existed and were able to exhibit photosynthesis that produced oxygen that spread across the atmosphere. Hence, consider the Theory of Spontaneous formation of organic molecules which suggests that the early earth had less to none oxygen. Thus, the atmosphere was abundant with the gases, CO2 and N2 with some other small amounts of H2, H2S, and CO. Hence, in Stanley Miller’s experiment when electrical sparks or “lightning” came in contact with these gases, the newly formed mixtures of CH4, NH3, and H2 were catalyzed. With these newly formed gases in interaction with H2O came the first synthesized some amino acids that compromised the earliest organic molecules which evolved to macromolecules, to be organelles of a cell. Which in the latter macromolecules are in today, maybe have been before the early nucleic acids (able to replicate) or proteins of these early cells.