Which of the Following Is Not True of Somatic Gene

Which of the following is not true of somatic gene therapy?

A) It's a proven technique to treat genetic disease in an individual.
B) The technique has proven potential to treat genetic disease in an individual.
C) It's somewhat risky because scientists can't completely control where the genes are inserted.
D) It's easier to use to treat "loss of function" genetic diseases, where a dysfunctional gene can merely be replaced by one that doesn't work.
E) It's expensive, so there may be somewhat limited access.