Answer:
The introduction
Explanation:
because it's the start of the whole process
a mild form of a disease that is put (injected) into a person or an animal’s blood using a needle (an injection) in order to protect the body against that disease..
This is a theme. The difference between those two is that the plot is similar to the storyline, whereas themes are general thoughts being analyzed. In this case, this is a theme, whereas something more detailed with description of events would be a plot.
