The diagram below shows homologous chromosomes during prophase I of meiosis. Which of the following correctly describes the process being illustrated?

a
Crossing over in which alleles are exchanged
b
Segregation of sister chromotids
c
Mutation in which the DNA content of the gene is altered
d
Condensation and segregation of alleles, Segregation of sister chromotids

a

Crossing over in which alleles are exchanged