An apple is cut into slices; half of the slices are sprayed with lemon juice, and the others are not. Slices are stored in a sealed plastic bag. After 4 days, they are observed to see how brown they turned. What factor is being tested in this experiment?
A. Effect of lemon juice on apple browning
B. Storage conditions for apple slices
C. Time-dependent changes in apple slices
D. None of the above