"What extracurricular activities were you involved in?"
If you don't have any work experience, then a company wants to know what extra activities you did in school to see if you are active. It is best to list a couple of things describing what the group is and what role you had in the group. If you were not a part of any group, it might be ok to make something up. It is hard to verify this so they will not find out. But it could back fire, if the interviewer happened to be in the same group at the same university.
Short Answers
"I was involved in our school newspaper. I was one of the writers for three years."
"I was very active in our university politics. In my senior year, I was the vice president of the University."
"Besides studying, I played baseball for our school. I really like to study and to stay physically active."
"I was involved with a group that helped awareness of environmental problems such as pollution. I was on a team that educated people about driving alternatives such as buses and carpooling."
Long Answer
"I was very active in the university magazine committee. I was a member of that group for four years. I helped write articles about events occurring in school. In my senior year, I was the editor and did less writing and more managing in regards to the magazine structure, what contents to add, and distributing work among the junior members of the group. I really enjoyed my experience there and learned about working closely together as a group to deliver a quality magazine."
If you don't have work experience, then you will need to say something to show them that you learned some valuable lessons such as team work. I suggest you to reflect on what you did during school and create a list of what you learned.