What is a psychologist? needs to be answered asap
1. a person who studies how the brain functions
2. a person who runs medical tests on the brain
3. a person who studies how people think, feel, and behave
4. a person who performs brain surgery

A psychologist is a person who studies how people think, feel, and behave

Explanation:

A psychologist studies normal and abnormal mental states, perceptual, cognitive, emotional, and social processes and behavior by experimenting with, and observing, interpreting, and recording how individuals relate to one another and to their environments.

fluid balance is an aspect of the homeostasis of organisms in which the amount of water in the organism needs to be controlled, via osmoregulation and behavior, such that the concentrations of electrolytes (salts in solution) in the various body fluids are kept within healthy ranges. the core principle of fluid balance is that the amount of water lost from the body must equal the amount of water taken in.