The two friends had a quarrel about money, but shortly afterwards they shook hands and _______.

--- I don’t know whether they did this ____ or by design. --- Who cares? They have to be punished. 

My uncle hasn’t been able to quit smoking，but at least he has ________.

—This teaching method seems good.—True. It can be __________ in a few selected schools to see how it works in practice.

As the quality of the city’s air continues to give rise to ______, the residents are encouraged to set off fewer fireworks.