Seed capsule shape in the weed "Shepherd's purse" is controlled by two independent genes C and D. The double recessive condition (ccdd) results in ovoid capsule shape. A dominant allele at either locus results in triangular capsule shape. What phenotypic ratio would result from crossing a double heterozygote (CcDd) with a double homozygous tester (ccdd)?
a. 1 triangular:15 ovoid
b. 1 triangular:3 ovoid
c. 9 triangular:7 ovoid
d. 12 triangular:4 ovoid
e. 15 triangular:1 ovoid