Here are suitable words to fill in the gaps for each sentence in the crossword:

1. **book** - I don’t want this book. Could you lend me the **book**?
2. **O** - **O** books give us a lot of fun. (Could be **"O"** as in an overview of various books, interpreted differently.)
3. **group** - Our teacher asks four of us to work in a **group**.
4. **playground** - The **playground** yard is very noisy at recess.
5. **author** - Do you know the **author** of this novel?
6. **enjoying** - My sister **enjoying** listening to music.
7. **exercise** - Do you think walking is a good simple **exercise**?
8. **couch** - Come on! Get up and go out! Don’t lie on the **couch** all the time!
9. **often** - How **often** do you go to the club? - Every Saturday.

Feel free to adjust any words based on the crossword layout!