Final answer:
None of the provided statements about crossing over are correct. Crossing-over increases genetic diversity and is not exclusively male, limited to certain chromosomes, or heterozygous genes.
Step-by-step explanation:
The correct answer regarding the statements about crossing-over is: e. none of these statements are true regarding crossing-over. Crossing-over is a process that occurs during prophase I of meiosis I, where there is an exchange of genetic material between non-sister chromatids of homologous chromosomes.
This exchange leads to new combinations of genes on each chromosome and is fundamental in increasing genetic diversity among gametes. It does not occur only in males, it is not limited to chromosomes with heterozygous genes exclusively, and it significantly enhances genetic variation rather than reducing it.