Most eukaryotes use meiosis as a type of cell division to produce reproductive cells, also known as gametes, this cells are used for sexual reproduction where they fuse together in a process known as fertilization. Somatic cells are diploid while gametes are haploid.
Diploid = 2 (n)
Haploid = n
If the gametes are haploid and contain 19 chromosomes (n= 19), somatic cells must have twice the number (2 * 19 = 38). Options A, B or C are not possible be.
It was during the Mitosis stage or the S-phase (Synthesis) of the Interphase. The cells spend most of their life in Interphase before Mitosis will occur.