几道逻辑题目不是很理解， 想请大家帮忙看一下，谢谢

cdstella

麻烦各位大牛帮我分析下以下三道题目
Prep08-42. 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 as 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 above depend on which of the assumptions
答案是A： People who have dieted down to a new weight tend to continue to consume substantially fewer calories than do people whose nomal weight is at that level.
我不明白为什么这个选项构成原题结论的必要条件，因为如果取非的话，就是胖子吃的卡路里和不减肥的人一样多，那么从题目来看是个无关选项，因为这不会加强和削弱结论。

Prep-08-65. Treatment for hypertension forestalls certain medical expenses by preventing strokes and heart disease. Yet any money so soaved amounts to only 1/4 of the expenditures required to treat the hypertension population. Therefore there is no economic justification for preventive treatment for hypertension.
Which of the following, if true, damaging to the conlcusion.
这个题目我不知答案是什么，不知道谁能告诉我下，谢谢

Prep08-66.The sustained massive use of pesticides in farming has two effects that are especially pernicious, First, it often kills off the pest's natural enemies in the area. Second, it often unintensionally gives rises to insecticide-resisitant pests, since thos insects that survive a particular insecticide will be the ones most resistant to it, and they are the ones left to breed.
From the passage it can be properly inferred that the effectivenss of the pesticides can be extended by doing which?
答案是B Periodically switching the type of insecticide. 但是这个做法怎么能解决杀死虫子的天敌这个问题呢，它只cover了第二个问题就是虫子的抗药性。
期待牛人解答，感激不尽～

bbmaker

第一题大概是这样的：原题中说胖人通常新陈代谢也慢，当他们通过比普通人少食卡路里达到减肥目的后，他们的新陈代谢依然很慢，如果他们瘦下来之后不再继续按照以前那种少食卡路里的饮食方式的话，和普通人一样摄入卡路里却消耗的少，脂肪堆积，他们就又会胖起来了
A的意思是：不会有胖子瘦下来之后继续摄入少卡路里（即延续减肥期间的饮食习惯），那么加上由于新陈代谢慢，消耗卡路里少，就推出了文中的结论therefore, ultimately regain weight until their body size again matches their metabolic rate.又胖了

一首简单的越歌

第二道题说的是be extended ，那么只要满足不杀死虫子天敌或者减少抗药性这两个条件的其中之一，就可以增强杀虫剂的效果。虽然不是完美方案，但如果其他选项更不靠谱，就只能选这个啦。

pemperley

第一题的选项A 你打错了吧 少一个否定 现在的A是个削弱啊