Fruit Color in a Particular Plant Is Controlled by a Set

Multiple Choice

Fruit color in a particular plant is controlled by a set of three QTLs (quantitative trait loci,or "polygenes") that work in an equal and additive manner.Each QTL has two alleles (i.e. ,A and a) ;each allele represented by a capital letter produces one dose of yellow pigment,while alleles represented with lower case letters do not produce any pigment at all.
-Assuming no effects by the environment,how many different shades of yellow fruit color are there?

A) 3
B) 7
C) 9
D) 12
E) 64