Alfonzo wants to prove to his wife, Sariya, that his preferred brand of paper towels is better than the cheaper store brand. In his determination to prove his point, he pours 1/4 cup of grape juice on the floor in two places side-by-side. He places brand A (his preferred brand) on top of one of the puddles and brand B (the cheaper store brand) on top of the other puddle. He leaves both towels on their perspective puddle for 30 seconds. After this Alfonzo excitedly exclaims to his wife that his brand is better because brand A absorbed almost all of the grape juice but brand B left more behind on the floor. Identify the independent variable.

a
cheaper store brand
b
30 seconds
c
grape juice
d
his preferred brand