That is because, during daytime hours, the concentration of NO2 in those cities was, on average, about 20% lower on Sundays.

这是因为在这两个城市的白天时段，平均下来周日的二氧化氮浓度要低大约20%。

youdao

That is because, during daytime hours, the concentration of NO2 in those cities was, on average, about 20% lower on Sundays.

这是因为在这两个城市的白天时段，平均下来周日的二氧化氮浓度要低大约20%。

youdao