用适当的单词,短语或句子补全对话

用适当的单词,短语或句子补全对话
Father:You have been working hard on your studies these days.
1.__________
Son:Yes,very tired.But I have to keep working hard.You know,the final exam is coming soon.
Father:I know it's2.____________to you.
Son:Yes,it's more important than any other exam.
Father:3._________But you don't need to worry about it.
Well,I don't worry about other subjects,but Chinese troubles me a lot.I'm afraid 4.__________.