Which of the Following Calculations Requires That You Utilize the Addition

Which of the following calculations requires that you utilize the addition rule?

A) Calculate the probability of black offspring from the cross AaBb × AaBb, when B is the symbol for black.
B) Calculate the probability of children with both cystic fibrosis and polydactyly when parents are each heterozygous for both genes.
C) Calculate the probability of each of four children having cystic fibrosis if the parents are both heterozygous.
D) Calculate the probability of a child having either sickle-cell anemia or cystic fibrosis if parents are each heterozygous for both.
E) Calculate the probability of purple flower colour in a plot of 50 plants seeded from a ?self-fertilizing heterozygous parent plant.