be scared of/be afraid of/be frightened of 在用法、含义上有什么区别?

e scared of------一下子的,突然的
be afraid of -------经常的,习惯性的
be frightened of ------一下子的,突然的
再问： 用法上呢？有没有具体的例句？
再答： 1 She is afraid of dogs.She daren't get close to them./ She doesn't dare to get close to them. 2 I was scared of the sight when he came in with blood on his face.== The sight scared me when I saw him come in with blood on his face. 3 The birds were frightened of the sudden noise and flew away== The sudden noise frightened the birds off. 请仔细阅读，反复思考，你就会悟出它们的区别。