善意的循环：牛奶与账单的故事
A boy was poor. He sold things door-to-door for money. One day, he felt very hungry. He asked a girl for water. She gave him milk instead. “It’s free,” she smiled.
Years later, the girl got very sick. Doctors couldn’t help her. Then Dr. Kevin, a famous doctor, treated her. After months, she got better.
The girl worried about the hospital bill. But the doctor said: “Bill was paid years ago with a glass of milk!” Dr. Kevin was the boy she helped long ago!