not only but also 与moreover 的用法

上海高考题中完形填空中有一句， Revision is not just an afterthought that gets only as much time as you have at the end of an assignment. ___56___, it is a major stage of the writing process, and writers revise every step of the way.
56. A. However B . Moreover C . Instead D . Therefore
空格里面答案填的是B moveover, 但是为什么不能选 C呢，
not....but, 确实是这样的，根据语义，应该选instead , 请高手分析下。谢谢

原句意是 ……不仅仅……而且……
如果用了instead就说不通了，就变成了 ……不仅仅……但是……？？
这样句意就表达不清楚了，希望我解释的你能够明白

the "just" told us everything. 再看看别人怎么说的。

B：表示更深一步的意义，“不仅如此”， C：可译为“实际并非如此，而是……”