阅读下面短文，在空格处填入一个适当的词或者使用括号中词语的正确形式填空。

    Earth Day is coming. Are there any activities on (protect) the Earth in your school? Well, in our school, we have such an activity (one) a month. For example, we want (plant) trees in the forest this month. We all know trees are very important our daily lives. They provide lots of (thing) for us. The forest is about two (kilometre) away, so we will walk there. There five groups of students and each group needs to plant thirty (tree). After that, we will take some (photo) there. I'm sure we will have nice day.