OG11 23请教maybe和probably的区别？

OG11 23

Of all the possible disaster that threaten American agriculture,the possibility of an adverse change in climate is maybe the more difficult for analysis.

A  is maybe the more difficult for analysis

B  is probably the most difficult to analyze

C is probably the most difficult for analysis

D is probably the more difficult to analyze

E is , it maybe the analysis that is most difficult

该题答案不难确定是B（根据最高级和difficult的用法）

但不明白的是 og中关于maybe和probably只提到这里必须用probably取代maybe，没有做任何解释

我不明白两者有什么区别，为什么该题中用maybe就是错呢？

有人帮忙解释一下吗？万分感谢！

probably 表示的可能性比较高

而且，maybe好像不能这么用的

一般在句首用maybe

因为possibility 吧？

以前OG10th的菜鸟手册上说maybe是比较口语化的表达，书面语应该用probably比较好

11th-2题出现了maybe和perhaps的比较  OG的解释是：maybe and perhaps are interchangeable; perhaps is slightly more formal