[tex] \: \huge \sf \blue {\fbox{ \green{Answer}}} \\ \\ \: \: \: \rightarrow \texttt{ c. an externality}[/tex]
Explanation:
The term "spillover" is typically associated with the concept of an externality, which is when the production or consumption of goods and services affects third parties who are not directly involved in the transaction. So, the correct answer is:
c. an externality
