The question is incomplete. The complete question is:
You cross a true-breeding red-flowered snapdragon with a true-breeding white-flowered snapdragon. All of the F1 are pink. What can you say about the alleles for the parental traits?
A. red and white are codominant
B. red is dominant
C. both red and white are recessive
D. red and white show incomplete dominance
E. pink is dominant, while red and white are recessive
Answer:
D. red and white show incomplete dominance
Step-by-step explanation:
Let's assume that the allele R is responsible for the red color of flowers in snapdragon while the allele W gives white-colored flowers. A cross between pure breeding red (RR) and white (WW) varieties obtains all pink-colored flowers (RW) in the F1 generation.
Cross: RR (red) x WW (white) = RW (pink)
Since none of the allele is able to mask the expression of the other allele in the heterozygous condition and the phenotype of the heterozygote is intermediate between that of the two pure breeding parents, it represents incomplete dominance.