Answer:
Crossing over happens when pairs of chromosomes pair up
Crossing over creates new combinations of genes on chromosomes.
Explanation:
The correct answer would be that crossing over happens when pairs of chromosomes pair up, exchange chromosomal segments, and create new combinations of genes on chromosomes.
Crossing over occurs during prophase I of meiosis when homologous chromosomes pair up to form a tetrad. Paired chromosomes then exchange chromosomal segments containing genes leading to a new combination of genes on each chromosome. Hence, the resulting daughter cells are genetically different from the original cell.