求问be able to和can的区别，附og上的一道题

Yulie_r

The methods proposed for reducing the amount of interest to be paid are not able to be used successfully without creating a problem of insufficient cash flow in the future.
A are not able to be used successfully without creating a problem of insufficient cash flow in the future.
B are not able successfully to be used without creating a problem in the future of insufficient cash flow
C cannot successfully be used without creating a future problem of insufficient cash flow
D cannot be used without succeeding in creating a problem in the future of insufficient cash flow
E cannot be used without succeeding in creating a future problem of insufficient cash flow

答案是C，我选的A，og的官方解释也很含糊，请问A有何不对？be able to和can的区别是什么？

小小豆豆酱

be able to do 发出动作的主语要是人，且后面一般不跟被动

machi929

A中的a problem of insufficient cash flow in the future有明显歧义
是发生在未来的现金流不足的问题？还是未来现金流不足的问题？

大脸猫leung

be able to 是表示'有能力'；can/could do 是表示'有能力'或者'有可能性'；在这个句子中个人觉得，intended meaning 应该是: the methods have no possibility of success，这里表示'有可能性'；如果套'有能力'的话，the methods have the ability to succeed ？？？，这样的话感觉改变了句子本身的intended meaning。因此个人觉得can/could do 在表示'有能力'的时候和be able to do 没有区别，但这个题是想说possibility的事情，所以cannot结构入选.