Question what effect can bottleneck events have on population that have nearly become

The answer is; D

It reduces the diversity of the population because some variations in the population can be completely eliminated by the bottleneck effect. Even if the population recovers in population size, the genetic variation will have reduced as compared to the initial population before the bottleneck. For a mall population, this effect can be grave because the reduced genetic variation may mean that the population may be unable to adapt to new selection pressures hence may go extinct.  

it's c. (to reduce the greenhouse effect/carbon gasses)

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides