[求助]T-9-Q27.GWD-10-Q37

T-9-Q27.
  大全987-606

Research during the past several decades on the nature of language and the processes that produce and make it understandable has revealed great complexity instead of underlying simplicity.

A.      that produce and make it understandable has revealed great complexity instead of underlying simplicity

B.       of producing and understanding it have revealed not underlying simplicity but great complexity

C.      by which it is produced and understood has revealed not underlying simplicity but great complexity (语意错了，变成语言是被过程产生和被过程了解的)

D.      by which it is produced and understood have revealed great complexity rather than underlying simplicity

E.     by which one produces and understands it have revealed great complexity instead of underlying simplicity

C错哪里了？

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

为社么选E呢？怎么用了is?why not B? 倒装句，动词单复数看后面的决定，后面是the rate, 所以动词用is