Jose is growing pea plants in his garden. He notices that some plants have green pods, while others have yellow pods. He researches the species he planted and finds that green pods are dominant to yellow pods.
According to Mendel's law (principle) of dominance, which of the following statements can be said with certainty?

I. The plants with yellow pods do not have an allele for green pods.
II. None of the plants with green pods has an allele for yellow pods.
III. The plants with yellow pods are displaying incomplete dominance.
IV. The plants with green pods might be homozygous or heterozygous for pod color.