Cystic fibrosis is often considered an autosomal recessive disorder, however, on a molecular level, it is actually codominant. Carriers of cystic fibrosis who are heterozygous for the disease produce both normal and defective CFTR proteins. Carriers do not exhibit symptoms of the disease because enough normal protein is created to prevent a build-up of mucus. ​ ​Which combinations of parents below have a possibility of having a child who is homozygous for cystic fibrosis? Select all that apply. A mother is CC and father is CC' B mother is CC' and father is CC' C mother is C'C' and father is CC D mother is CC and father is CC E mother is CC' and father is C'C' F mother is C'C' and father is C'C'