求教大牛 这题实在是不懂

shmozart

GWD-10-Q37:GWD-11-26
On Earth, among the surest indications of sunspot cycles are believed to be the rate that trees grow, as seen in the rings visible in the cross sections of their trunks.

A.    On Earth, among the surest indications of sunspot cycles are believed to be the rate that trees grow
B.    On Earth, among the surest indications of sunspot cycles are, it is believed, the rate of tree growth
C.    On Earth, the rate at which trees grow is believed to be among the surest indications of sunspot cycles
D.    Among the surest indications on Earth of sunspot cycles, believed to be the tree growth rate
E.    Among the surest indications on Earth of sunspot cycles is believed to be the rate at which trees grow

answer 是E,why not C?我的困惑在as seen 上，这个 as seen是什么意思，又省略了什么成分呢？谢谢！

zwc1990125

非牛，互相学习。首先看句意啊，看懂 as seen in the rings visible in the cross sections of their trunks.修饰的肯定是rate啊，E把他倒过来就是为了让rate和它更近不会有修饰歧义。