Researchers Studying the Effects of Alcohol Consumption Assessed the Physical

Researchers studying the effects of alcohol consumption assessed the physical coordination skills of 21-year-old men. Prior to the assessment, each participant was randomly assigned to drink a beverage with either 4, 2, or 0 ounces of alcohol.
-In this study,what is the independent variable?

A) the age of the research participants
B) the amount of alcohol consumed
C) the physical coordination skills of the research participants
D) the length of time between drinking the beverage and the assessment