Researchers Who Were Studying Memory Had Participants Learn a List

Multiple Choice

Researchers who were studying memory had participants learn a list of words after consuming a soft drink with caffeine or a decaffeinated version of the same soft drink.The researchers then counted the number of words that were recalled from the list.In this study,what would you call the type of beverage (caffeinated or decaffeinated)

A)  extraneous variable 
B)  dependent variable 
C)  confounding variable 
D)  independent variable