大全的解释： 985, 天山-02
Kaplan gmat 800上答案是A 解释抄录如下：
The key to getting the right answer for this question is recognizing that the underlined portion of the sentence should not contain pronoun. The answer choices give you the option of replacing with different colors with whose different colors but the second option is wrong because, if you added whose, it could refer to thelayers or the Canon, and whenever a pronoun has more than one possible antecedent (the thing it refer to), it's used incorrectly. Eliminate (B) and (C). (A) is correct. Eliminate (E) as well because the subject of "marking" is similarly unclear; is it the layer or the Canyon this is marking the passage of time? And (A) is better than (D) because, once again, see is better than the wordier alternative been able to see. (A) is correct A中“,with different colors that mark”感觉应该理解成状语修饰主句或者说就是修饰前面的动词seen。参考og113或大全915。
B, C的whose修饰不清。
D的able to多余; 如果with different colors marking是个独立主格结构表原因, 将这个结构还原 because different colors mark the passage of time like the rings, those who have visited the Grand Canyon have typically
been able to see layers of sediment in the gaping canyon, 但mark和be able to see没有明显的因果关系; 如果
because layers’ colors marking the passage of time like the rings is different, those…been able to see….意思上可能合理。
E中marking修饰不清。 | 
