A parasite could determine the size of the population. Whether it grows or shrinks. It could also change genetics
The right answer is Haploid cells join to form an organism that has a complete set of chromosomes.
Meiosis makes it possible to pass from a cell to 2n chromosomes to 4 cells with n chromosomes, thus ensuring the passage from the diploid phase to the haploid phase.
So from the fertilization phase to the meiosis phase, the cells will be diploid (2n chromosomes). From the meiosis phase to the fertilization phase, it is the haploid phase (n chromosome).