Gene S Controls the Sharpness of Spines in a Type

Multiple Choice

Gene S controls the sharpness of spines in a type of cactus. Cacti with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cacti have dull spines. A second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. Which of the following explain why a crossing a true breeding spineless cactus with a dull-spined cactus could result in both sharp- and dull-spined offspring?

A) Gene S genotype is pleiotropic
B) Sharp-spined cacti are more successful in environments with predators
C) The spineless cactus was heterozygous at the S locus
D) Gene N genotype is polygenic