–Mom, may I go swimming with my friends in the river?–No, you _________. That’s too dangerous.
---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.
It’s said that _____ of the water around the world _____ polluted.