The couple was their lost child.

Li Yang: Good morning, Mathew.

Mathew: Good morning, Li Yang.

Li Yang: There's still smog today. We'll have to go to school with face masks (口罩).

Mathew:  According to the news, PM 2.5 pollution is the main problem with air pollution.

Li Yang: Yes, and air pollution may do harm to people's health.

Mathew: So the Chinese government and Chinese people must take action to fight against it, Li Yang:

Mathew: Since PM 2.5 is mainly caused by vehicles (机动车) and factories, cars with large emissions (排放) should not be allowed and factories should be closely watched.

Li Yang:  We hope that more and more people will join us in making the blue skies return for good.

Mathew:

Listen, my friend. It's in the past.