The correct options are
A A technique used to replace a defective gene with a healthy gene
B A technique that corrects the defective gene
C A technique used to cure genetic disease
Gene therapy is used to treat genetic disorders resulting due to the presence of a nonfunctional gene copy. In this case, functional genes are inserted into the cells or tissue of a patient and then those cells are delivered to the patient to compensate for the effects of the non-functional gene.