你们学校多久升一次国旗?
in your school?
The teachers welcome their students (polite) at the school gate every morning.
After doing sports for months, Tina is becoming (thin) than before.
Forty (year) development has changed Huai'an into a modern city.
To my surprise, my uncle got his driving licence in his (fifty).
Andrew often does DIY with different (knife) in his free time.