The correct option is A mitosis; meiosis
Mitosis is the process by which a diploid cell divides to give rise to two identical diploid daughter cells.
In our body, when dead cells are replaced, the new cells being formed need to be identical to the old ones. That is, they must have the same chromosome number. Thus, dead cells in the body are replaced by mitosis.
Meiosis is a type of cell division that occurs in the reproductive cells of sexually reproducing organisms. This reduces the chromosome number by half, resulting in the formation of haploid daughter cells. The gametes formed in our body are haploid cells. Hence, during gametogenesis, a diploid cell undergoes meiosis to generate haploid gametes.