Sc On Earth, among the surest indications of sunspot cycles

[qq.wangyaqi]

[u]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
I have trouble reading the structure of this sentence, Is the answer C or E?
Thanks!

[shah.abhilash]

a)the sentence says as if the tree is growing rate(wrong).

b)use of 'are' and then just one reason to state is wrong. Also rate is singular. We cannot use are.(wrong).

c)Got potential.

d) A run on sentence. some preposition must be there. even if a preposition is used the sentence will still not make sense.(sense).

e)This sentence starts with modifier "Among" and just states one reason.This is a bit awkward. Consider this:
Among all the friends i know , Jhon is the quietest..
Jhon is the quietest among all the friends i know.
the 2nd part is easier to read and is better.

Si i go with C. i can be very sure the ans is C. Option E just does'nt sound right :-).(Not a very good method in GMAT to eliminate ans but here i am sure it's worth taking the risk )