_ _ _ _ _ _ _  refer to the benefits (or harms) a firm or an individual causes to another  for which they are not paid (or penalised ).

Externalities

The correct answer is option (3) : Externalities

Externalities: Those benefits or harms accruing to another person, firm or any other entity which occur because some person, firm or any other entity may be involved in an economic activity. If someone is causing benefits or good externality to another, the latter does not pay the former. If someone is inflicting harm or bad externality to another, the former does not compensate the latter.