阅读A. B、C、D四篇材料，然后从各小题所给的四个选项中选出最佳选项。
Sam was a fifteen-year-old boy living with his little sister, Julie. Their parents had passed away long ago. Sam had taken care of Julie by himself.
One day, Sam woke up at three in the morning as usual. When Julie was sleeping alone, Sam left their little house to send newspapers. When he found an old man sitting in front of their house, Sam was so surprised that he stopped to look at him closely. It was an icy morning and he looked very cold.
The poor old man didn't have anything to cover himself with. Sam went into his house to get the old man a blanket（毯子）, However, there were no extra（额外的）blankets, so Sam thought hard and took his father's coat. It was the only thing of his father's that he had left Sam wrote a short note, "Sir, I found you sleeping in front of my house. This is my father's coat. I hope it fits you well. "He put the note in a pocket of the coat, and covered the old man with the coat. Then he went to work. When he came back three hours later, both the man and the coat were gone. Sam thought that it was the best thing he could have done with his father's coat.
That afternoon. Sam hurried home after school because Julie was at home alone. However, Julie and the old man were standing in front of the house, and Julie shouted to Sam, "Brother! He's our grandfather!"
The grandfather smiled and said, "Sam, thank you for giving me the coat and letting me know how good my grandson is. This coat was the one that I gave my son a long time ago!"