The study of organisms living in rivers or lakes is known as what?

Explanation

The correct answer is freshwater biology. This field specializes in studying organisms that inhabit freshwater environments like rivers and lakes. While microbiology focuses on microorganisms generally, it does not specifically address the freshwater environment. Marine biology is concerned with marine environments such as oceans and seas, not freshwater. Social biology looks at the social behaviors of organisms, which can occur in any environment and are not specific to freshwater ecosystems.