GWD3-Q40

Two centuries ago, Tufe
                Peninsula became separated form the mainland, isolating on the newly formed Tufe
                    Island a population of Turfil sunflowers.  This population’s descendants grow to be, on average, 40 centimeters shorter than Turfil sunflowers found on the mainland.  Tufe
                Island is significantly drier than Tufe
                    Peninsula was.  So the current average height of Tufe’s Turfil sunflowers is undoubtedly at least partially attributable to changes in Tufe’s environmental conditions.

Which of the following is an assumption on which the argument depends?

1. There are no types of vegetation on Tufe
                           Island that are known to benefit from dry conditions.
2. There were about as many Turfil sunflowers on Tufe
                       Peninsula two centuries ago as there are on Tufe
                           Island today.
3. The mainland’s environment has not changed in ways that have resulted in Turfil sunflowers on the mainland growing to be 40 centimeters taller than they did two centuries ago.
4. The soil on Tufe
                           Island, unlike that on the mainland, lacks important nutrients that help Turfil sunflowers survive and grow tall in a dry environment.
5. The 40-centimeter height difference between the Turfil sunflowers on Tufe
                           Island and those on the mainland is the only difference between the two populations.                                                                        （C）

不是太理解，请达人指点！

LZ能不能把你不理解的选项讲的更具体一些？

C取非削弱，典型的假设题。如果大陆的环境变化，使大陆上的花发生了变化的话，那么就不能说是海岛上的气候导致迁移到海岛的花朵发生了矮化的变化。起到了削弱的作用，所以选项就是它了。

假设是因为大陆的气候没有变,就排除了大陆气候变导致两者不同的情况了.就说明是岛上的气候导致两种植物的差别了.

我认为这算是一种排除他因吧

说得有点乱,不知道lz看不看得明白

environmental condition和mailand environment的区别是什么呢

我怎么感觉c是与原文相反的呢