When sodium and chlorine atoms come together to form sodium chloride (NaCl), they transfer an electron. ... Because the sodium ion has a positive charge, and the chlorine ion has a negative charge, they are attracted to each other, and form an ionic bond.
The correct answer should be something like: "Gene therapy involves the use of bacteria or viruses to deliver new or modified genes to cells". That is what can be concluded based on the paragraph you provided.
