How does mendel’s work demonstrate support for the concepts of dominant and recessive alleles?

The correct answer for this question is this one: "
Mendel shows that dominant alleles always took over, while sometimes in the F2 generation recessive traits would come back. As you can see, from the proportions of phenotypes in the offspring. Then, if given that the genes would be equal you would get 1/4 A, 1/4 B and 1/2 AB; but you often get 1/4 A and 3/4 B.