. Everyone must have known the death of the waitress,________?
We are still at the airport. If it weren’t for the delayed flight, we _____ the concert right now.
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.