In an effort to reduce the amount of fat and the number of calories that they consume, many citizens of the United States are making significant changes in their diets. For them staying in shape and looking fit now take precedence over eating foods that are filling and that taste good. It is likely that if they maintain these new priorities with consistent regard for other health issues, the length and quality of their lives will increase significantly. Which one of the following is an assumption upon which the argument is based?
Eating foods that are filling and tastes good is inconsistent with staying in shape and looking fit.
Examine the question: Assumption is an obvious key word. According to the passage if people maintain the new priorities (changes in diet), the length and quality of their lives will increase. The subsidiary conclusion is that people are making changes to their diets because they'd rather be fit than eat foods that are filling and taste good. The gap between these two statements is that better diet is linked to longer life and changes to diet means not eating filling, tasty food. Going by the process of eliminationoption (b) is irrelevant. If anything, this weakens by suggesting that changes in diet aren't enough. Option (c) is irrelevant. This goes along with the general idea, but it's not strictly necessary. In option (d), the time of discovery is irrelevant. In option (e), the goals of most citizens are irrelevant. You're only interested in the people who are acting on their goals. Option (a) fills in the assumption needed to make the subsidiary conclusion true. If eating filling, good tasting foods is inconsistent with staying in shape and looking fit, people who want to stay in shape and be fit are willing to give them up. They will maintain good habits and live longer, better lives. Hence option (a) is the correct answer.