CR Bible 题的难度是？看不懂啊，求大神指点迷津

Elihu2

本人英语基础并不好，现在看OG的题到可以理解，可最近在看大牛们推荐的CR Bible（PowerScore Gmat CR Bible）感觉里面说的好绕。。不是完全懂得赶脚。 里面附的少量的题做了做，感觉很难把握住meaning啊，各路大神们指点迷津。
附上Bible里面的题：(精简了一点)

Weaken题

scientists study modern-day primates in an attempt to better understand the behavior and lifestyle of their now-extinct primate ancestors. This is a questionable technique, however, as primate groups have not always been exposed to the same types of external stimuli. Most primates now being observed have been seriously impacted by the loss of their former habitat due to deforestation.

感觉看这篇时，大体意思懂一点：科学家研究现代灵长类动物为了更好的理解他们已灭绝祖先的生活和行为方式。然而，这个研究存在技术问题，由于动物们并不经常受到相同的刺激？ 大部分的这类动物因为砍伐失去栖息地而长期受到影响。

但，分逻辑关系时就懵了~ 不知道那个是 conclusion 哪些是 premises

Bible 上的题大多是这种感觉~~  大神求教啊

Elihu2

大神们都在哪里啊