FastMart, a convenience store chain, is planning to add pancake syrup to the items it sells. FastMart stores do not have shelf space to stock more than one variety of syrup. Surveys of FastMart customers indicate that one-fourth of them prefer low-calorie syrup, while three-fourths prefer regular syrup. Since FastMart' s highest priority is to maximize sales, the obvious strategy for it is to stock regular syrup. Which of the following, if true, most seriously weakens the argument? ['People buying pancake syrup at convenience stores, unlike those buying it at supermarkets, generally buy it only a few times.', 'Regular syrup does not sell for a higher price per unit than low-calorie syrup.', 'Sales of syrup are not expected to account for a large proportion of total dollar sales at the average FastMart store.', '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.']