Critical Reasoning

Last year a chain of fast-food restaurants, whose menu had always centered on hamburger, added its first vegetarian sandwich, much lower in fat than the chain's other offerings. Despite heavy marketing, the new sandwich accounts for a very small proportion of the chain's sales. The sandwich's sales would have to quadruple to cover the costs associated with including it on the menu. Since such an increase is unlikely, the chain would be more profitable if it dropped the sandwich.

Which of the following, if true, most seriously weakens the argument?

A) Although many of the chain's customers have never tried the vegetarian sandwich, in a market research survey most of those who had tried it reported that they were very satisfied with it.
B) Many of the people who eat at the chain's restaurants also eat at the restaurants of competing chains and report no strong preference among the competitors.
C) Among fast-food chains in general, there has been little or no growth in hamburger sales over the past several years as the range of competing offerings at other restaurants has grown.
D) When even one member of group of diner's is a vegetarian or has a preference for low-fat food, the group tends to avoid restaurants that lack vegetarian or low-fat menu options.
E) An attempt by the chain to introduce a lower-fat hamburger failed several years ago, since it attracted few new customers and most of the chain's regular customers greatly preferred the taste of the regular hamburger.


OG 2017 New Question

This question asks us to weaken the conclusion. What is the conclusion? It is: the chain would be more profitable if it dropped the [vegetarian] sandwich.

Why? Because it is unlikely that sales will quadruple, the amount needed to cover the costs of including the sandwich on the menu.

What's the assumption? The argument seems to assume that the sandwich provides no benefit to the restaurant's profitability except through sales of its own.

Answer choice (D) attacks this assumption. If four people want to eat out, and one is vegetarian, the group will avoid restaurants that do not offer vegetarian cuisine. Accordingly, while the sandwich may not be profitable itself, it does provide value to the restaurant as without this sandwich, the restaurant might lose four potential customers.

I understand what you said. But, I can not determine why option A is not right? It also weaks the argument.