C. Compare Homozygous dominant (purebred, GG), homozygous recessive (purebred gg), and heterozygous (hybrid, G?

Well, alleles are the Letters which determine which traits will be expressed in future generations. Most traits have Dominant and recessive genes. The dominant genes will be expressed in dominant homozygous (purebred GG) and heterozygous (Gg). The Recessive genes will be expressed if both recessive alleles are present (homozygous gg). P.S. homozygous means containing both of the same allele, and heterozygous means containing one dominant and one recessive allele.

If you want to predict the offspring, each letter has a 50% chance of one allele being passed on (the other 50% coming from the other parent organism). For the homozygous, it is an 100% chance of their recessive/dominant allele being passed down; for heterozygous, it is 50/50 (has both alleles). You must also look at the other parent to see what possibilities are.