阅读下列材料，从每题所给的A、B、C、D四个选项中选出最佳选项。
One day, a young man was taking a walk with a professor(教授). As they went along, they saw a pair of old shoes lying on the road. They thought the owner of the shoes must be a poor man who worked on the farm nearby. The student said to the professor, "Let's take away his shoes, and hide (躲藏) ourselves behind those trees and wait to see what will happen when he cannot find them. That must be very interesting."
"My young friend," answered the professor, "we should never make fun of others who are poor. But you can put a coin (硬币) into each shoe, and then we will hide ourselves and watch what change (变化) will happen to him."
The student did so, and they went to hide themselves behind the trees.
The poor man soon finished his work, and came back. When he was putting on his coat, he put his foot into one of his shoes. He felt something hard and found the coin. Surprise was seen on his face. He found the coin and looked at it again and again. He then looked around, but there was no person. He now put the money into his pocket (口袋). When he put on the other shoe, he was surprised again to find the other coin. He fell on his knees (膝盖), looked up to the sky and said aloud some thanksgiving words to the person who gave him the coins.
The student stood there, and his eyes were full of tears (眼泪),"You have taught me a lesson that I will never forget. Now I understand: ▲ ,"he said.
he was sick. Then he only knows the people in the room with him. Every morning, he gets up, has breakfast, and then goes back to bed to listen to the radio. Often he forgets that he has done these things. Sometimes he has breakfast three times in the morning.