When I was in trouble, he often gave .

—Maybe these songs can bring them peace.

—You'd better go to see a dentist at once.

    A new study found that people's lives are made shorter in North China. It showed the life expectancy (平均寿命）had been cut down by 5.5 years there. Scientists think that it is because of the heavy air pollution. It is really the truth. Our country has already done something. However, it doesn't seem to work so well.

    "Air pollution is bad for people's health. The harm is much more serious than we can imagine, said Chen Yuyu of Beijing University, one scientist of this study.

    There was serious smog and haze in Beijing in November 2016. The sky was gray and the air smelt strange. Heavy haze covered the city. Highways were closed and planes couldn't take off on time. People couldn't see things clearly even within 15 meters in some places. Some primary schools were closed for several days.

    We should all fight against air pollution and think of good methods to solve the problem. People should be encouraged to take buses, ride bicycles or walk instead of driving cars. The factories that pollute air heavily should be closed.

    "It might be expensive to improve our environment, but we must do it. Protecting our environment means protecting ourselves," Li Hongbin, another scientist, said.