准确地说应该是 I am afraid not to do = I am afraid (that) I can't do
　　【解析】be afraid 后面可以跟一下几种结构：
　　1、介词 of 短语,如：
　　　　He is afraid of his own shadow.（他连自己的影子都害怕.）
　　2、不定式短语（肯定式是 be afraid to do,否定式是be afraid not to do）.如：
I'm afraid to be late.我可能要迟到了.
I'm afraid not to be invited.我恐怕不会受到邀请.
　　3、that 引导的从句（that 可以省略）
I'm afraid (that) I'm wrong.恐怕我错了
I am afraid (that) you don't see my point.恐怕你还没有明白我的意思.
　　只要行为者既是 be afraid 的主语又是不定式的逻辑主语或从句的主语,不定式和从句是可以互相转换的.如：
　　不定式转换为从句——
肯定句：I'm afraid to be late 可以转换为 I'mafraid I’ll be late.我可能要迟到了.
否定句：I'm afraid not to be invited.可以转换为 I'm afraid I will/can not be invited.
　　从句转换为不定式——
肯定句：I'm afraid I’m wrong 可以转换为 I'm afraid to be wrong.
否定句：I am afraid (that) I don't see yourpoint 可以转换为I am afraid not to see your point.
　　至于从句中是用 do not、will not 还是can not/could not 需要视语境的情况而定.

第一题没答案，答案应该是不允许的。如：No,
you
mustn't.
第二题A。句中已经有谓语，所以后面不能用ride了。只能是介词短语。
第三AC都有可能，如果你题目没有抄漏掉，倾向选A。希望得到肯定回答。如果后面出现些消极的词汇，例如：I'm
afraid
not.则选C。
你这应该是初中的题目吧。

I am afraid not
恐怕不行（可以）
双语对照
例句:
1.
The coolest job in the american mind, I am afraid not completely consistent with thechinese people.
在美国人心目中最酷的职业，恐怕与中国人不完全一致。

2.
Please tell me this is a prank, dewey. I am afraid not, sid. Come on.
请告诉我这是一个开玩笑，杜威。我恐怕不，锡德。跟我来。

I've always been afraid lf heights.我一直害怕恐高。
She was afraid for her children.她为她的孩子们担心。
（that从句）They were afraid that their teacher would find out.他们担心老师会发现 。
(表sorry)I'm afraid you've completely misunderstood the question.恐怕你完全误解了这个问题。
I'm afraid that we can't come this evening after all.恐怕我们今晚依然无法前来。
“Was she impressed with our work?” “I&#dnsNR39;m afraid not.”“她赞赏我们的工作吗？” “恐怕不。”
不知道亲还满意不。。。