Explanation
The observation seeks an explanation for the increase in restaurant sales despite the expectation that higher parking rates might discourage customers who require short-term parking.
A. If private parking lots are more expensive than on-street parking, it does not directly explain the increase in restaurant sales; it suggests an additional cost burden on customers.
B. Owners' opposition to the parking rate increase does not provide an explanation for the increase in sales.
C. The parking habits of business staff do not directly relate to customer behavior or sales at restaurants.
D. (Correct Response) If more expensive parking leads to greater turnover in cars parked in front of the businesses, it could mean that more customers are coming in and out, potentially accounting for the increase in restaurant sales.
E. Competition with malls offering free parking would more likely decrease, not increase, restaurant sales in the business district.