根据情景内容，在空白处填入合适的单词。
A: Today is Earth Day. I’m doing an interview to (1)________ (2)________ how people are celebrating it. Hi, guys. Do you know today is Earth Day?
B: Yeah. Of (3)________.
A: So, (4)________ do you celebrate Earth Day?
B: Well, I use less electricity than usual.
C: I do two things to celebrate. First, I observe a zero carbon day. Second, I plant a tree. It’s a lot of fun, as well as helping the environment.
A: So, how do you spend the zero carbon day?
B: I walk or ride a bike (5)________ I go.
C: I think every day should be Earth Day.