这里给你列几个：

1. ABPeoplePickerNavigationController-ChatKitAdditions
2. ProgressiveMimeParser
3. NSString-MimeEnrichedReader
4. MobileAccessoryUpdater
5. ProgressiveMimeParser
6. SMTPAccount

上面提供的是iOS6中的。
这里有7.0之前各个版本的私有API头文件下载。 链接描述

I think they just want you to explain what private APIs are instead of asking how many are there?

http://stackoverflow.com/questions/17580251/what-exactly-is-a-private-api-and-why-will-apple-reject-an-ios-app-if-one-is-us

提供个 github 地址：

https://github.com/nst/iOS-Runtime-Headers