Mr Chen __________ his mobile phone to the shop because it can’t work at all.
----How about the pollution in the countryside?--- Luckily, it's not as serious as _______ in the big cities.
---Someone is knocking at the door. Who may it be?---It ______ be Tom. He is still in the school.
Lucy had few close friends. So she didn’t know ________ about the trouble.
Her singing lessons her five hours a week.
He can’t state clearly how long he has ___________ the bicycle?