Answer:
Option d)Vaccines allow for building immunity without harmful exposure because not all viruses are safe to be exposed to.
Step-by-step explanation:
The concept of a vaccine was started by Edward Jenner. This was after a smallpox vaccine was successfully carried out on a patient on a farm. A vaccine, is a special replica of the bacteria or virus that is inoculated into the patient's body to activate the immune system. As the "bacteria" multiplies, the body produces special and specific body cells to target the organism. This produces the active acquired immunity that is needed to protect the person from future attacks by the organism in life.