按字母表顺序排列的一组字母是 。
---It _____ ten years since we _____ last time. ---Yes. How time flies!
---Why don't you go hiking today? ----I prefer ______ at home to ______out because the weather is too bad.
---How many Chinese astronauts ______ into space since 2003? ----Twelve , including two women.
---Who helped you clean the classroom yesterday? ---_______. I did it all by myself.
I remember ______ the math problem ______.But I can’t remember it’s answer.