Which situation is a result of crossing-over during meiosis?
 A
 Genes are duplicated exactly, ensuring that offspring will be
 identical to the parents.
 B
 Chromatids thicken and align themselves, helping to ensure
 genetic continuity.
 с
 Genes are rearranged, increasing the variability of offspring.
 D
 Chromatids fail to sort independently, creating abnormal
 chromosome numbers.