Probably the strongest argument for using gene therapy and genetic enhancement appeals to the principle of: a. justice. b. double effect. c. beneficence. d. autonomy.

C. beneficence.D. autonomy.

The strongest argument for using gene therapy and genetic enhancement appeals to the principle of both beneficence and. Autonomy.
in beneficence the idea addressed is our actions should promote good and doing good is thought of as doing what is best for the patient. 

In autonomy, the person has the ability to make his or her own decisions.

could you go a bit more in depth with you question? it's quite hard to understand. as soon as you do that i will be glad to : )