A Cross of a True-Breeding Smooth Pod and Yellow Pod

A cross of a true-breeding smooth pod and yellow pod plants results in all smooth pod offspring. This indicates that

A) yellow is dominant and smooth is recessive.
B) smooth is dominant and yellow is recessive.
C) yellow and smooth are not alleles.
D) yellow and smooth are variants of the same gene.
E) two of the answers are correct. Yellow and smooth are variants of the same gene, and smooth is the dominant trait.