An accountant for a store is interested in comparing sales before and after an ad campaign. She expects a change in sales following the campaign. The hypotheses would be:
a. Null Hypothesis: No change; Alternative Hypothesis: Change
b. Null Hypothesis: Change; Alternative Hypothesis: No change
c. Null Hypothesis: Increase; Alternative Hypothesis: Decrease
d. Null Hypothesis: Decrease; Alternative Hypothesis: Increase