请教：can和be able to的区别

“>”＝“优于”

can/be able to > ability of sb. to do (one's ability to do sth.) > capable of doing > capability to do sth.

can 强调事物的可能性；could 是 can 的一般过去式。

be able to 强调人所具备的能力，不能用被动语态 (be able to be done ×) OG243

-able构成的形容词,应该表达事物的特征,

cannot be done 或 could not be done 是动作的强调，原来是动作的强调，就应用原来的动作强调。