例 1 [ 结果 ] These plants are termed opportunists because [ 原由 ] they rely on their seeds ’ falling into settings where competing plants have been removed by natural processes, such as along an eroding riverbank, on landslips, or where a tree falls and creates a gap in the forest canopy.
A. Because [ 原由 ] their seeds grow in places where competing plants are no longer present, [ 结果 ] dandelions are classified as opportunists.
B. [ 结果 ] Dandelions are called opportunists because [ 原由 ] they contribute to the natural processes of erosion and the creation of gaps in the forest canopy.
C. The term opportunists apply to plants whose seeds fall in places where they can compete with the seeds of other plants.
D. The term opportunists apply to plants whose falling seeds are removed by natural processes.
有学生会问，后面的 such as 要怎么处理。一般我们有个原则，在句子当中假如是补充的数据，那很关键 ; 假如是重复的数据，应该是不关键的。所以看 such as 只要明白一点，它究竟给前面的什么内容举例。看例子的内容，会发现说的都是地方，说明是给 setting 举例，那样就能够把它放在一边。
于是，我们明白作者原句的意图是在解释有因果的关系，那样四个选项中正确的答案必然在逻辑关系和讲话的意图上和原句是一样的。发现 A、B、C、D 中仅有 A 和 B 是有因果的，再进一步看具体的内容，可知 A 的原由和结果都与原句一致，为正确选项。例 2 [ 转折前 ] Estimates indicate that the aquifer contains enough water to fill Lake Huron, but unfortunately, [ 转折后 ] under the semiarid climatic conditions that presently exist in the region, rates of addition to the aquifer are minimal, amounting to about half a centimeter a year.
A. Despite the current impressive size of the Ogallala aquifer, the region ’ s climate keeps the rates of water addition very small.
B. Although the aquifer has been adding water at the rate of only half a centimeter a year, it will eventually accumulate enough water of fill Lake Huron.
C. Because of the region ’ s present climatic conditions, water is being added each year to the aquifer.
D. Even when the region experiences unfortunate climatic conditions, the rates of addition of water continue to increase.
这个题目原句中有一个 but unfortunately，说明这句话前后有一个转折，那样它最核心的意义是作者前后表示的不同。
看转折前：aquifer 地下蓄水层还有足够的水来填满休伦湖。尽管我们不清楚休伦湖有多大，但你明白作者的意图是说水 许多。
转折后：在这个半干旱的条件下，补充率很小。Amounting to 后面给出补充率的数字，是重复内容不关键。
所以明确转折前说水量大，转折后说补充率小。然后我们看四个选项，正确答案肯定在逻辑关系的表达上是跟 But 属于同一个范畴。A 有 despite，表示转折、让步 ;B 有 although，让步 ;C 有个因果，原文没有存在因果 ;D 有 even 表示让步。所以在四个选项中我们会优先考虑 A、B、D 这三个选项。
仔细看 A 选项，despite 后的内容表示水量大，和原句转折前同样 ; 而逗号后的内容表示补充率小，和原句转折后同样。所以 A 是正确选项。例 3 Numerous insects occupy the marsh, feeding on living or dead cordgrass tissue, and redwing blackbirds, sparrows, rodents, rabbits, and deer feed directly on the cordgrass.
A. Insects feed only on dead cordgrass, while most other marsh inhabitants feed on live cordgrass.
B. The marsh is a good habitat for insects, but a relatively poor one for birds and animals.
C. Although cordgrass provides food for birds and animals, it gives insects both food and a place to live.
D.Cordgrass provides food for numerous insects, birds, and other animals.