The correct answer would be option D, Positive Externality.
Samantha is given a flu shot by her doctor. This reduces the probability that she will get the flu and it also reduces the probability that other will get the flu too. The latter is an example of a Positive Externality.
Explanation:
When someone consumes something, and that consumption gives benefit not only to him, but to others as well, then the benefits gained through that consumption are called as the Positive Externality.
For example when vaccinations and use of medicines limit the spread of some disease to others, other people are benefited by your use of vaccination. This benefit is the Positive Externality.
So when Samantha got the flu shots, not only she was cured but others also now have less chances of getting flu from her.
Learn more about Positive Externality at:
https://brainly.com/question/10743687
#LearnWithBrainly