Here are the suitable words to fill in the gaps based on the crossword puzzle with "O":

1. **book**
2. **comic** books give us a lot of fun.
3. Our teacher asks four of us to work in a **group**.
4. The **outdoor** yard is very noisy at recess.
5. Do you know the **author** of this novel?
6. My sister **enjoys** listening to music.
7. Do you think walking is a good simple **exercise**?
8. Come on! Get up and go out! Don’t lie on the **couch** all the time!
9. How **often** do you go to the club? - Every Saturday.

Feel free to modify any if needed!