Ответ:
1. People do risk because they get pleasure from it.
2. People go trekking the mountains to work in team, develop their body and spirit.
3. Trekking in the mountains dangerous, because it's height, steep slopes, where you can stumble and fall down.
4. I think people feel absolutely happy, when they go a long and hard way and finally reach the top.
5. Maybe, they want new sharp feelings (thrill).
6. It's dangerous, because your parachute may not open.
7. I think it's euphoria, fear and happiness together.
8. They want to get extreme.
9. Whitewater rafting is dangerous, because your boat can crash in any moment.
10. I think they are scared.