Answer:
The correct answer is C. An internal cost
Explanation:
An internal cost is cost the internal struggle that is going on within oneself. Unlike external cost, it is not paid through material things, rather it is paid by internal mental strategies.
This is an example of an internal struggle because the roommate cannot be categorized into a third party, and it is your internal struggle that you cannot focus while there is noise. For some people, noise helps to concentrate.
Therefore, it would be considered as the internal cost that you pay due to your roommate.
