23. When the sperm cell then meets the egg, the 23 chromosomes that each sex cell have form the 46 total chromosomes that each human being has.
Alleles can disappear from a population through natural selection. This relates to the most fit phenotype because the breed with the desirable trait, or the most fit, will live and produce off spring. Eventually the less desirable trait and its corresponding allele will disappear after multiple generations pass. If the environment does not change alleles of non desirable traits will disappear. <span />
Because of all the air pollution i THINK IS THE ANSWER
The answer to this question is option D