D. In general, customers who prefer regular syrup will buy low-calorie syrup if regular is unavailable, but those who prefer low-calorie will not buy regular syrup. The original passage is about comparison between low-calorie syrup and regular syrup. D means low-cal syrup will be a good substitute for regular ones to capture the entire group of customers. But selling regular ones only will lose 1/4 of the customers. C might work as assumption, not weaken. "does not sell for a higher price per unit " might mean equal price or much cheaper. But common sense tells us regular syrup usually will not cost lower than 1/3 of the low-cal ones. |