--- It’s the fourth time that heavy smog(雾霾) has hit the city this month.--- It’s high time we _______ measures to fight air pollution. 

I was about to leave my house______ the telephone rang.

_________ that it's very cruel to kill wild animals for money.

In recent years travel companies have succeeded in selling us the idea that the further we go, ________.

---Tom has been fired by his boss． ---              ? As far as I know, he is a hardworking and considerate fellow．