In cats, orange vs black fur is controlled by a single x-linked gene. The orange and black alleles are codominant; the intermediate phenotype is tortoiseshell.
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A mother and father cat have 6 kittens: two orange females, two tortoiseshell females, and two black males.

a. What is the mother cat's phenotype?
a) black
b) orange
c) tortoise shell
d) impossible

b. What is the father cat's phenotype?
a) black
b) orange
c) tortoise shell
d) impossible

c. What is the fourth possible phenotype for their offspring?
a) black female
b) orange male
c) tortoise shell male
d) they already had all the offspring with possible phenotypes