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
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
research确定了A或者C项，根据新东方，not..but 优于instead of,但是答案选A ，哪位帮忙解释下？ | 
