Answer: B. the social benefit from consuming the good to be greater than the private benefit.
Step-by-step explanation:
A POSITIVE EXTERNALITY is one where the benefits are enjoyed by a third party as a result of an economic transaction.
Even though the third parties can be considered to be freeloaders, this externality is encouraged because it has such a larger social benefit which surpasses even private benefit.
For example, a student graduating from a university with skills they learnt there and contributing to society.