Refer to the Following Information to Answer the Questions Below

Multiple Choice

Refer to the following information to answer the questions below.
Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all.
-The relationship between genes S and N is an example of

A) incomplete dominance.
B) epistasis.
C) complete dominance.
D) pleiotropy.
E) codominance.