Gene therapy, which includes the correction of defective genes, is a significant part of the human genome project. Which of these is an application of the technique?
A) A new protein, which can repair defective genes, is injected.
B) Mutated DNA sequences, which can pair with existing genes, are introduced.
C) The DNA sequences of the entire genomes of disease-causing microbes are compared.
D) A new gene, which codes for the protein that can repair defective genes, is introduced.