Hello,
The answer is option A a gene is inserted to remove mutated DNA.
Reason:
Its option A because something that is not use in genetic engineering is a gene that is inserted to remove a mutated DNA. Its not option B because a gene removed is part of genetic engineering. Its not option C because a gene is that is inserted to make a mutation inactive is part of genetic engineering. Its not option D because genetic engineering can indeed cause or create another gene.
If you need anymore help feel free to ask me!
Hope this helps!
~Nonportrit