GWD13-Q27

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

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

请问为什么不选择C呢？

多谢大家！

对，答案是A

貌似A是主动，C是被动。还有补充吗？