-- Gravity causes forces of attraction between masses.
-- Every molecule of every component of our atmosphere has mass.
-- Gravity causes forces of attraction between the molecules of the
atmosphere, which may largely be disregarded, but more importantly
between the molecules of atmosphere and the Earth.
In other words, gravity has the effect of keeping the atmosphere in place
around the Earth. Without gravity, there would be no atmosphere.
(There would be no Earth either, but that's another story.)
Wow.. Alexander the Great.... I remember learning about him... Any ways to answer your question your answer would be possibly D.. if i am incorrect then I am truly sorry.
Moose since most live freely and are not feed and maintained by humans