Which statement BEST explains why populations of humans are rarely in Hardy-Weinberg equilibrium?
Select one:

a. Movement of humans among populations protects against the effects of chance events on allele frequencies.

b. Recessive traits do not disappear over time because they are hidden in heterozygous humans.

c. Not all humans in a population have an equal chance of survival and reproduction.

d. Mutation is the most significant source of variation in human populations.