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. -If doubly heterozygous SsNn cactuses were allowed to self-pollinate, the F₂ would segregate in which of the following ratios?
A) 3 sharp-spined:1 spineless B) 1 sharp-spined:2 dull-spined:1 spineless C) 1 sharp-spined:1 dull-spined:1 spineless D) 1 sharp-spined:1 dull-spined E) 9 sharp-spined:3 dull-spined:4 spineless