Answer:
The correct answer would be when gametes are produced.
In diploid (2n) organisms, meiosis is used to produce haploid (n) gametes.
Meiosis is a reduction division which results in the production of four daughter cells from a single parent cell and each of the daughter cell contains only half the chromosomes present in the parent cell.
Thus, if parent cell is 2n then gamete would be n.
It helps in maintaining the chromosome number through generations.