No one will be sad because humans will have learnt to fix many of the problems that affect us now, like war, pollution and hunger, ________ ?
Be careful when you cross this very busy street. If not, you may _____ run over by a car.
My teacher _____ me the key to the classroom but I’m afraid I _____ it.
---John and Tom, you two clean the classroom today, _____? ---But we cleaned it yesterday.
Pleasant as they made it ______ in Jiuzhaogou, we felt tired after the long journey.
Although the police thought he was the most likely one, _____ they had no exact proof about it, they could not arrest him.