Sentence Correction (SC) | On Earth, among the surest indications of sunspot cycles are believed

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
...

---