Sure! Here are the completed sentences with the correct forms of the words provided:

1. Why do so many **teenagers** like using Facebook and TikTok nowadays? (TEENAGER)
2. Mr. Joe is a famous architect and he has won a lot of awards for the **buildings** he designs. (BUILD)
3. The little boy is very **untidy**, so his bedroom is always really messy. (TIDY)
4. Elephants are **intelligent** creatures and they enjoy interacting with human beings. (INTELLIGENCE)
5. To be **honest** with you, I don't really like the new neighbor because he is so talkative. (HONESTY)
6. The meaning of a message can have **different** examples of text language. (DIFFERENCE)
7. Doing martial arts can help us become stronger and more **confident**. (CONFIDENCE)
8. The children have to use their **imagination** to come up with a new story right away. (IMAGINE)
9. Doing crossword puzzles is one of the most **challenging** jobs for my son. (CHALLENGE)
10. An intelligent person is always good at learning and **understanding** things. (UNDERSTAND)

Let me know if you need further assistance!