The beautiful song ________ me of those happy old days we had spent together.
Not until I came home last night ________ to bed.
Work hard when young, ______ you will regret.
It’s hot in the shopping mall, because the air-conditioning system ______.
--- 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.
Science has given clear evidence ______ smoking can lead to many diseases.