Ответ:
1. I was bored because the book was boring.
2. My parents are worried because the situation is worrying.
3. He was excited because the party was exciting.
4. They were tired because the trip was tiring.
5. My classmates were interested because the lesson was interesting.
6. I am relaxed because the music is relaxing.
7. We are excited because the match is exciting.
8. They were bored because the film was boring.