There are twenty­eight classes in our school，______ over 56 students.

Mr Black has two sons, one of ________working as a doctor.

With food and gunpowder       short, the soldiers are suffering from hunger and danger of being attacked by the enemies at any time.

_______ more trees being cut, huge quantities of good soil are being washed away into the Yellow River.

With more people _____ the traffic rules, our city is becoming better organized.