A vaccine uses a live pathogen that is too weak to make you sick. Once it enters your body you defeat it easily. Now that yur body is familiar with it your body can fight off the disease in the future.
"The set of observable characteristics of an individual..." is what i found on google, so i'm guessing its a.
hope this helps :)
Answer:
How does the bird's long beak help it survive?
Explanation:
It could be to crack nuts or to help dig up bugs. This should work unless the question needs to be about cells and stuff.
Answer:
they mutate and become immune to modern medicine
Explanation:
