Answer:
B. true, because immunity is nonexcludable, and everyone can simultaneously enjoy the "herd immunity."
Step-by-step explanation:
When a lot of people get vaccinated against a disease, the chances of spreading of that disease drastically decreases in the population. Even if someone is not vaccinated against that disease, their chances of contracting it are low because other people are vaccinated and hence its incidence rate in population is low. This phenomena is called as herd immunity. For example: 19 out of 20 people should be vaccinated against measles to protect the non vaccinated ones.
Herd immunity benefits the entire public and is considered a classic public good. It is nonexcludable which means that someone can not be excluded from being benefited by it. Two people residing in the same population will reap the benefits of herd immunity even if the degree of benefit might be different.