Answer:
e.) If exposure to cowpox gives immunity to smallpox in milkmaids, then milkmaids have a natural immunity and their blood should be used to develop a smallpox vaccine.
Step-by-step explanation:
- Milkmaids who suffered from cowpox did not suffer from smallpox i.e. they were immune to the disease.
- If milkmaids did not suffer from smallpox then there must be some element of immunity that they received once they had recovered from cowpox, this would likely be found in their blood as antibodies.