In pea plants, the allele for tall plants is dominant to the allele for short plants. if a homozygous tall plant is crossed with a homozygous short plant, what percent of their second generation of offspring would you expect to be short?
a. 25 percent.
b. 0 percent.
c. 50 percent.
d. 100 percent

If a homozygous tall plant is crossed with a homozygous short plant, the percentage of their first generation of offspring that you can expect to be short is 50%. But, here we need the second generation, so you just half that number, and the correct answer should be A. 25 percent. 
Think of it as humans - if one of your parents has blue eyes, and the other brown eyes, you have 50/50 chance to have either blue or brown eyes. However, your child is going to have 25% chance to have either of those eyes, provided that your partner doesn't have the same eye color as you.