Answer:
some traits become more common, others less. ... The traits that become more common are the ones that are “adaptive” or “increase fitness” (that is, a creature's chances of living longer and producing more offspring).
H2+1/2O2-->H2O
since there are two atoms of hydrogen present in the reactants and in the product you don't need to add any number before H2
we add 1/2 before O2 because only 1 atom is needed for the water molecule
Fermentation enables cells to produce chemical energy from the breakdown of sugar
The correct answer is b, antigens
