Due to .......... rapy changes would be heritable.

Gene therapy is treating the diseases by modifying the gene expression or inserting the deficient gene therapeutically into the patients cells. Gene therapy is of two types, somatic gene therapy and germline gene therapy.

In somatic gene therapy, gene manipulation is done in the cells which will affect the patient but it will not be inherited. In germline gene therapy, gene manipulation is done in the germ cells or the gametes that will be used to conceive. The modified germ cells will produce the gametes having the inserted gene and on fertilisation will produce a zygote that will form the individual in which each and every cell will have the manipulated gene, because every cell descendes from the zygote. Thus, the changes will be heritable.

So, the correct answer is C.