Answer :
C. when parental units form reproductive cells, the source cells undergo meiosis and split into four gametes, each containing half of the original cell's genetic information (the split happens haphazardly so no two gametes are the same). Thus, each fertilized egg contains equal amount of genetic information from each parent.
C: each child receives only half of each parent's genes
There is a process called meiosis. Meiosis deals with sex cells dividing. They divide then fuse together to create new traits (phenotypes). We know that humans have 23 pairs of chromosomes.
In the first stage, the chromosomes replicate and form chromatids. Then they will line up in the center to the cells into pairs and cross genes, which creates new gene combinations. This crossing of genes makes each child different unless you are an identical twin.
Hopefully this helps somewhat. I didn't write about the whole process, just about the part that hopefully does an okay job of explaining how siblings could look so different.
