story: One day Joe was upset. His father told him that they would go on a motorcycle trip. They decided to go when Joe turned 21. When Joe was 21 he and his father bought motorcycles. The had a great trip together.
 selected sentence: When Joe was 21 he and his father bought motorcycles.
Joe and his father want to go on a motorcycle trip >Motivates> Joe and his father buy motorcycles when Joe turns 21