又一道SC

princess

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.)
C. by which it is produced and understood has revealed not underlying simplicity but great complexity

书上答案是A，可以我觉得A中produce后面应该补上it，否则有歧义
不知道C有什么错误（除了它用的是被动语态）

谢谢指教

zyh79

c答案我觉得by用错了，要用也只能用in
a答案就看怎么理解produce了，我也觉得produce常用作及物动词，那么这样就会和后面的make并列，并产生歧义。所以，只有把它理解为不及物动词了。