Which method offers the most reliable way of assessing whether athletic performance is boosted by drinking soda with caffeine in it? the survey the experiment naturalistic observation the case study?

The correct answer is the experiment. 

An experiment or experimental design in research studies refers to when a researcher manipulates and controls a variable (known as an independent variable) in order to determine its effect on other variables. In this instance, a researcher could assess whether athletic performance is boosted by drinking soda with caffeine in it by providing some athletes in the research study with a caffeinated soda and the remaining athletes with non-caffeinated soda. After this, the researcher can then find out whether the athletes who consumed the caffeinated soda had an improved performance compared to the participants who consumed non-caffeinated soda.