In 1950's, stanley miller and harold urey showed how organic molecules necessary for the formation of life could be assembled from simple molecules known to have existed on earth millions of years ago.

evidence from miller and urey's experiments suggest that complex organic molecules could be formed from other, simpler molecules. why is it unlikely that this process is still occuring today?

a) modern amino acids are unlike those that may have existed on the ancient earth.
b) the current environment of the earth is too polluted to allow the formation of organic molecules.
c) the present day earth lacks sufficient energy to allow the formation of organic molecules to occur.
d) living organisms such as bacteria are likely to interfere in the process by breaking down the organic molecules.