I hope so 我希望如此,用于交际
比如：--- Maybe you will be better tomorrow!---I hope so.
I hope that-从句 比如：I hope that they can come to my help.我希望他们会来帮我.
I am afraid so...恐怕如此,恐怕这样,用于交际
比如 --- Not many students can pass the exam.---- I am afraid so.
I am afraid -that -从句 I am afraid that I can't lend you the book because I am reading it myself.
恐怕不能借这本书给你,因为我自己在看!