It's tree planting time!

　　大家一起來(lái)植樹(shù)！

　　Lingling remembers that it's tree planting this weekend.

　　玲玲記得這周的活動(dòng)是植樹(shù)。

　　Please write about the effect of tree planting on air in a city.

　　請寫(xiě)寫(xiě)植樹(shù)對城市空氣的作用。