The difference between gene therapy and other forms of genetic engineering is A) Gene therapy involves placing genes from individuals of one species into an
individual of the same species.
B) Gene therapy is a new branch of genetic engineering.
C) Scientists have been much more successful using the techniques of gene therapy
than the scientists working in other area of genetic modification.
D) Gene therapy involves replacing damaged genes with helping genes.

D) Gene therapy involves replacing damaged genes with helping genes.

Explanation:

Mutations are spontaneous changes that occur within DNA. These can be somatic, occurring in body cells, or germline, in gametes. Some mutations are harmful or deleterious, affecting an individual's ability to survive or quality of life.  

Thus, therapeutic methods involving altering harmful genes or their products were created. These are a form of genetic modification, which involve multiple biotechnological applications and techniques.  However, genetic engineering specifically uses recombinant gene technology.