For each of her pregnancies, state the probability that this couple will have a child who is:
a) Homozygous normal: 1/4, Heterozygous: 1/2, Homozygous sickle-cell: 1/4
b) Homozygous normal: 1/2, Heterozygous: 1/4, Homozygous sickle-cell: 1/4
c) Homozygous normal: 1/2, Heterozygous: 1/2, Homozygous sickle-cell: 0
d) Homozygous normal: 1/4, Heterozygous: 1/2, Homozygous sickle-cell: 1/4