Elian is testing his hypothesis that the more ripe an orange is, the more Vitamin C it contains. He takes four oranges of varying degrees of ripeness and squeezes
samples of juice from each one. He then measures the concentration of Vitamin
C in each sample of orange juice. He systematically adds a measured amount of
a chemical called a titrant into the orange juice, waiting for its color to change.
When its color changes, he knows that the amount of Vitamin C present in the
juice is equal to the amount of the titrant he has added, which he can
calculate. What does Elian think is the independent variable in this experiment?
A: orange ripeness
B: amount of titrant
C: color of the solution
D: amount of Vitamin C per orange