Подскажите почему слово prevented пишется через окончание ed, в предложении: people hoped that with the help of the declaration, wars would be prevented.

Это страдательный залог. действие совершается над предметом

Today i want to tell you about my favorite music band imagine dragons. it was founded in 2008 in las vegas. in 2009, the group begins to work in a studio. soon, they were invited to perform at an annual festival, as "the most demanded group of 2010" on the local radio. they released two soundtracks: «who we are» for the film "the hunger games: catching fire" and " battle cry" for the film " transformers: the era of extermination." i can not say whose performance in the group i like more. it's impossible.

1. He is a doctor.
2. How is your father? He is fine.
3. We are pilots.
4. My father is an engineer.
5. Is this fox little? Yes it is.
6. Where are you from? I am from Russia.
7. Her uncle is a worker.
8. That elephant is gray.
9. How are you? I am fine.
10. The big balls are on the table.
2)
1. This fox is little.
2. The little hares are in the box.
3. How is your brother? He is fine.
4. Where are they from? They are from America.
5. Those horses are brown.
6. They are engineers.
7. My mother is a doctor.
8. Is her aunt is a teacher? Yes, she is.
9. That bear is in the bag.
10. Are they from Great Britain? Yes, they are.