Which of the following best describes the approach that was used in the first gene therapy trial for treating SCID?

a. The normal ADA gene was introduced by injecting liposomes directly into the patients’ bodies.

b. Lymphocytes were removed from a SCID patient, the normal ADA gene was transferred into the lymphocytes via liposomes, and then the lymphocytes were returned to the patient’s body.

c. Lymphocytes were removed from a SCID patient, the normal ADA gene was transferred into the lymphocytes via a retrovirus, and then the lymphocytes were returned to the patient’s body.

d. None of the above describe the approach used in the trial.