The correct answer is C. sewage discharge.
Even though there might even be no harmful pathogens at all if there isn't any waste, it is correct because it is implied that there is waste such as fecal matter inside of the sewage discharge.
Interspecific competition
A type of competition in which organisms belong to different species compete with each others for same resources.
Example
Leopard and lion.
intraspecific competition
A type of competition in which organism belong to same species compete with each others for same resources.
Example
birds for breeding or shelter compete with each others
chlorine because it has 7 electrons on the outer shell
