---         does she do on weekends?--- She usually helps her mother.

—______ is it from Olympic Center to your school? — It’s about 10 minutes’ walk.

—I don't think we have met before，________？—Yes，once at a party，but we weren't introduced.

—Do you know the boy?—_______. He’s Bob’s brother, Bill.

---John and Tom, you two clean the classroom today, _____? ---But we cleaned it yesterday.