Answer:
C. The introduction of a new gene that can bind with the abnormal gene to inhibit its action.
Explanation:
Gene therapy is a new system of treatment being introduced that employs the use of genes as against drugs in the treatment of diseases. Most diseases arise as a result of a mutation in a gene. Gene therapy seeks to replace these mutated genes with healthy genes. The bad gene could also be inactivated or knocked out to prevent further damage.
So, when a new gene is introduced and made to bind with an abnormal gene to inhibit its action, that is a knockout process employed in gene therapy. The practice is still under trial.