Answer:
a.When an organism is heterogeneous for a trait, it expresses only the dominant allele
b. A child will be born with CF only if they inherit one CF gene from each parent. A person who has only one CF gene is called a CF carrier. They are healthy and don't have the disease. But they are a carrier of the disease.
Step-by-step explanation:
a.In other words, the dominant trait always masks the recessive trait.
b.A parent can be a CF carrier, and pass the CF gene on to their child.