Option 1: Killed germs - This option suggests that the smallpox vaccine involves introducing killed germs into the body. However, this is not accurate. The smallpox vaccine does not use killed germs.

Option 2: Weakened germs - This is the correct answer. The smallpox vaccine involves introducing weakened, or attenuated, germs into the body. These weakened germs are still alive, but they are not as strong or infectious as the wild-type smallpox virus. By introducing weakened germs, the vaccine stimulates an immune response in the body, without causing the full-blown disease.

Option 3: Live antibodies - This option is incorrect. Antibodies are produced by the body`s immune system in response to infection or vaccination. They do not need to be introduced directly into the body as part of the vaccination process.

Option 4: Activated germs - This option is incorrect. The smallpox vaccine does not involve introducing activated germs. It uses weakened germs instead.

Overall, the smallpox vaccine utilizes weakened germs to stimulate an immune response in the body and provide protection against smallpox.