According to Mendel's law of segregation, the segregation of the alleles takes place. This segregation occurs during

A

Pollination

B

Embryonic development

C

Seed formation

D

Gamete formation

Mendel's law of segregation deals with the formation of gametes and their random fusion. He explains in law of segregation that the allele pairs separate or segregate during gamete formation.
This was well explained by the crossing of F1 heterozygotes which yielded 3:1 ratio for dominant to recessive trait.