The government ______ air quality in urban areas from levels one to five: excellent, fairly good, slightly polluted, poor and dangerous.
At the meeting, the old man ________ some good advice about bringing down the market price of housing.
It is nice to hear from a close friend. ________, we last met more than thirty years ago.
It is his horse, according to the old man, ________ saved him from the trap.
Do you have any difficulty ________?
21st Century is ________ a newspaper. It helps us to improve our English a lot.