请教T-9-Q27

为什么这样啊

Research(主语)during the past several decades on the nature of language and the processes that produce and make it understandable has revealed（谓语） 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

为什么不能选C, 答案是A

猪王山

被动语态会显得很罗嗦，og上面经常这么说
而且not...but...结构让这个意思表达的很不简洁