I believe the answer is: positive externality
Positive externality refers to The benefit that enjoyed by a third party when the first and second party are conducting a transaction.
When you receive a vaccines, you prevent yourself from becoming a host that could contaminate other people from getting the virus. In the example above, you and your children are the first and second party. And other children are the third party.
Differences between culture and architecture
It would be the last choice. <span>They are stored for later use.</span>
The answer is B, because the Song would make all government candidates undergo the civil service exam. Only if they passed would they be able to become part of the bureaucracy.
