It is already well understood___________ causes the global warming.

Can you believe I had to pay 50 yuan for ahaircut—–You should try the barber’sIgo. It’s only 10.

I hear the government is going to ___ the air quality with the new standard PM2.5，isn’t it—Yes, ___ the air pollution will get more serious.

_____ you please play tennis with me —Sorry, I _____.

The house rent has been growing fast in cities. You have to pay nearly _______ than you did two years ago for a flat of the same size in some cities.