Answer:
<u><em>The correct option is D. All alleles are either dominant or co-dominant.</em></u>
Explanation:
Due to his contribution to genetics, Mendel is known as the father of genetics. The Law of Segregation and Law of Independent Assortment formulated by Mendel lay the foundation of genetics. Even today, advances are made in the field of genetics, based on these laws. Mendel's studies showed some traits to be dominant and others to be recessive.
However, Mendel was not able to detect the factor of codominance in his studies. The factor of codominance was studies later.
