根据对话内容，从下面方框中选择适当的单词填空，使对话内容完整正确。
Reporter：Can you introduce something about your latest class activity?
Monitor：Sure. The students from our class planted some lines of trees on March 12th, 2008.
Reporter：How did you plant trees?
Monitor：First, the students were 小题1: into groups of four. Next, each group of students planted a tree. Then, they poured some water over the trees.
Reported：How do you 小题2: for the trees?
Monitor： We plan to come back and look after the trees 小题3: .
Reported：Sounds good. Could you tell me why you choose to do that?
Monitor：As you know, pollution has become one of the most serious 小题4: . We would like to try our best to improve our environment.
Reporter：Well, it’s very meaningful. If everyone can do something to protect the environment 小题5:, our city will become much more beautiful.
