请问NN：GWD-10-Q37

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

答案是E，Among the surest indications on Earth of sunspot cycles这句的主语应该是indications, 怎么用单数啊？另外on Earth 改变位置是否影响整个句子的意思？我觉得E的表述为什么要把on Earth放在indications of之间？请NN帮忙解释一下

可以把E转换成
(The rate) among the surest indications on Earth of sunspot cycles is believed to be the rate at which trees grow .主语中的the rate和后面的"the rate at which ..."重复故可以省略，故排除A/B.

as seen in the rings visivle in the cross sections of their trunks 用as的平行原则排除C.

D没有谓语.