Where is oxygen content in a river or stream likely to be highest?
a.
the source
b.
the mouth
c.
the middle portion
d.
none of the above

What discovery would weaken the primordial soup hypothesis of the origin of life? question 19 options: lightning was common on early earth. earth’s early atmosphere contained carbon dioxide, water, and trace gases. earth’s early oceans were warm and shallow. asteroid impacts were uncommon when life is presumed to have begun.