Dietician: "Recent Studies Have Shown That People Can Lose Weight

Dietician: "Recent studies have shown that people can lose weight solely by changing their diet alone, without having to increase their amount of activity. In two recent studies, overweight but otherwise healthy people cut their caloric intake and all participants lost weight without having to change their activity level, showing that weight loss through diet alone is possible."
Critic: "That is not true. While some people may have been successful, the study only covered otherwise healthy people who were likely to succeed. What about other people, who have tried to change their diets without exercising, and failed to lose weight?"
Which of the following is the best evaluation of the critic's argument?

A) The critic misses the point entirely, so resorts to an ad hominem attack on the dietician.
B) The critic shows that the results would have different if the studies had included more people.
C) The point at issue is only to show that something is possible, not to show that it will work in every case.
D) The critic demonstrates that the studies are not relevant for most people.
E) The critic assumes, without justification, that the studies were conducted by fraudulent researchers.