请教大全986

1.                  Those who have visited the Grand Canyon have typically seen layers of sediment in the gaping canyon, with different colors that mark the passage of time like the rings in a tree trunk.  

(A) seen layers of sediment in the gaping canyon, with different colors that mark

(B) see layers of sediment in the gaping canyon, whose different colors mark

(C) been seeing layers of sediment in the gaping canyon, whose different colors are markers of

(D) been able to see layers of sediment in the gaping canyon, with different colors marking（D）

(E) seen layers of sediment in the gaping canyon, marking by different colors

这道题目的问题有两个问题:

1.be able to 表示一次性的动作,为什么在这里却是用have been able , 为什么have seen不好

2.似乎在后半部分的指代都不好,D中的with 难道不会修饰谁, 不应该是those吗?

请大家给出意见

没有人有意见?先谢过大家了....