Answer:
C. Condensation and segregation of alleles crossing-over in which alleles are exchanged.
Step-by-step explanation:
Notice that the two chromosomes are crossed at the bottom in the first image. This indicates that they are "crossing-over."
Once this happens, alleles are exchanged. The result is that each chromosome now has an allele from the other one. Notice how at the end, the chromosomes now have a different color on the bottom tip and a letter that was given to them by crossing over.