【一道GMAT语法改错题，关于定语从句的Researchduringthepastseveraldecadesonthenatureoflanguageandtheprocesses“thatproduceandmakeitunderstandablehasrevealedgreatcomplexityinsteadofunderlyingsimplicity”.A.thatp】

　　一道GMAT语法改错题，关于定语从句的

　　Researchduringthepastseveraldecadesonthenatureoflanguageandtheprocesses“thatproduceandmakeitunderstandablehasrevealed

　　greatcomplexityinsteadofunderlyingsimplicity”.A.thatproduceandmakeitunderstandablehasrevealedgreatcomplexityinsteadofunderlyingsimplicityB.ofproducingandunderstandingithaverevealednotunderlyingsimplicitybutgreatcomplexityC.bywhichitisproducedandunderstoodhasrevealednotunderlyingsimplicitybutgreatcomplexityD.bywhichitisproducedandunderstoodhaverevealedgreatcomplexityratherthanunderlyingsimplicityE.bywhichoneproducesandunderstandsithaverevealedgreatcomplexityinsteadofunderlyingsimplicity原题中“”符号中粗体字是划线部分，我选的C，答案是A，答案是说C的which从句用了被动语态，按照主动优先原则，排除C因为主语是research，所以后面的谓语肯定是has，所以BDE肯定不对现在想问的是：C本身有错吗？修改部分produceandmakeitunderstandable这里是不是定语从句？（限定theprocesses）若是定语从句，那么GMAT考试有个原则就是介词+which要好于用where、when等，为何这里不选择用C？A中的it指的是什么？