Prep 2 Q42

愁死了，看了3M的解释，还是不懂。。。。整个都绕不清楚。。。多谢同学们帮忙看看吧！！！

42.   (32943-!-item-!-188;#058&007554)

Researchers have found that when very overweight
people, who tend to have relatively low metabolic rates, lose weight primarily
through dieting, their metabolisms generally remain unchanged.  They will thus burn significantly fewer
calories at the new weight than do people whose weight is normally at that level.  Such newly thin persons will, therefore,
ultimately regain weight until their body size again matches their metabolic
rate.

The conclusion of the argument above depends on
which of the following assumptions?

(A) Relatively few very overweight people who have
dieted down to a new weight tend to continue to consume substantially fewer
calories than do people whose normal weight is at that level.

(B) The metabolisms of people who are usually not
overweight are much more able to vary than the metabolisms of people who have
been very overweight.

(C) The amount of calories that a person usually
burns in a day is determined more by the amount that is consumed that day than
by the current weight of the individual.

(D) Researchers have not yet determined whether
the metabolic rates of formerly very overweight individuals can be accelerated
by means of chemical agents.

(E) Because of the constancy of their metabolic
rates, people who are at their usual weight normally have as much difficulty
gaining weight as they do losing it.

题干 胖人新陈代谢慢 而且通过节食变瘦以后新陈代谢还是和原来一样慢 因此他们变瘦之后和正常体重的人相比燃烧的卡路里少很多（这里有一个暗含的推论 减肥后的胖人必须比正常体重的人少摄入很多卡路里才能保持减肥后体重） 结论就说胖人减肥以后还是会恢复到原来的体重以匹配他们的新陈代谢速度

只有如果胖人减肥后还一直坚持节食（也就是减少卡路里摄入）那么才能保持减肥后目前的体重 （保持体重--〉节食）把这句话做逆否等价转换 就变成下一句

只要他恢复原来的卡路里摄入量 他的体重就会反弹 （不节食--〉体重反弹）（后一句是题干结论，前一句是充分条件）

有一句比较拗口的话，假言命题的充分条件是推理的必要条件 这么说可能比较难理解 我来举个例子

如果我说这么一句话“他不吃饭就会死 所以他死了” 这样的说话肯定大家都会觉得莫名其妙吧 要使这个推理成立 那么我必须先说“他不吃饭” 因此，“他不吃饭”就是“所以他死了”这个结论的必要条件

现在回头再看那句红色的话 把它代回题干去 题干变成  因为 “只要胖人恢复原来的卡路里摄入量 他的体重就会反弹” 所以“胖人的体重会反弹” 现在让你找assumption就很容易了吧 就是“只要胖人恢复原来的卡路里摄入量”

前面半句就是题干整个推理的必要条件 正好符合A选项的意思