Which of the Following Statements About Gene Replacement Therapy Is

Which of the following statements about gene replacement therapy is accurate?

A) Gene replacement therapy is a treatment for genetic disorders that has been widely used since the early 1970s.
B) Gene replacement therapy is a highly controversial treatment that is not used because of the ethical concerns.
C) Gene replacement therapy is a treatment currently used with cystic fibrosis patients to attempt to override the effects of the cystic fibrosis genes.
D) Gene replacement therapy is an experimental treatment for chromosomal abnormalities and is seldom successful.