When certain medium height hybrid plants were crossed, they produced offspring that were dwarf, ...

When certain medium height hybrid plants were crossed, they produced offspring that were dwarf,
  medium, and tall in a ratio of 1 : 2 : 1. This is an example of:
  a. variegation.
  b. hybrid vigor.
  c. incomplete dominance.
  d. epistasis.
  e. a polygenic trait.

Question 2

Calico cats are never male because:a.
   recessive genes are not usually expressed on their X chromosome.
  b. male hormones prevent expression of the calico phenotype.
  c. two different X chromosomes are needed for the expression of the calico phenotype.
  d. two different Y chromosomes are needed for the expression of the calico phenotype.
  e. one X chromosome and one Y chromosome are needed for the expression of the calico
  phenotype.