Given three possible phenotypes for parents showing dominance (AA, Aa, aa), which combination would produce a 1:2:1 ratio of genotypes and a 3:1 ratio of phenotypes?
I. AA x Aa
II. Aa x aa
III. Heterozygous x Heterozygous
IV. Aa x Aa
V. Homozygous dominant x Heterozygous
A) I, II, III, IV, and V only
B) III and IV only
C) I and V only
D) II only