What happens a few days after fertilization?

C

Explanation:

I took biology in tenth grade

Between four to six days after conception, the fertilized egg will develop into a blastocyst and burrow into the uterine lining, attaching itself firmly. In this early stage, the embryo develops a yolk sac, which provides its first nutrients. But as the tiny being grows, it will turn to its host (you) for sustenance

Explanation:

The answer will be B

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).

the answer to your question is tooth decay.