Решение:
Образуем существительные от данных прилагательных или глаголов.
- "I don't think you understand the seriousness of the problem," he said.
- Tom is going to stay in a new luxury hotel next to the beach. Development
- Ian thanked his hosts for their kindness.
- We play board games on long journeys for amusement.
- At the end of my holiday, I always feel a bit of sadness about leaving a place.
Ответ: seriousness; development; kindness; amusement; sadness.