阅读下面短文，从每题所给的A、B、C、D四个选项中，选出能正确回答所提问题或完成所给句子的最佳答案。

     Sixteen years ago, a boy gave me an important gift. It was a smile.

      It was the early autumn of my first year at a middle school, and my old school was far away. As a result, no one knew who I was. I was very lonely, and afraid to make friends with anyone.

     Every time I heard the other students talking and laughing, I felt my heart break. I couldn't talk with anyone about my problems.

Then one day, my classmates were talking happily with their friends, but I was sitting at my desk unhappily as usual.  At that moment, a boy entered the classroom. I didn't know who he was. He passed me and then turned back. He looked at me, with a smile.

    Suddenly, I felt the touch of something bright and friendly. It made me feel happy and warm. That smile changed my life. I started to talk with other students and made friends. Day by day, I became closer to everyone in my class. The boy with the lucky smile has become my best friend now.

    One day I asked him why he had smiled, but he couldn't remember doing so!

     It doesn't matter because all the dark days have gone. I believe that the world is what you think it is. If you think it is lonely, you might always be alone. So smile at the world and it will smile back.

根据材料内容，选择正确答案。

    At midnight Mr. King coughed again. He got up and took some medicine. Before he lay down again, he smoked. And he couldn't go to sleep any longer. He found the medicine book and began to read it. He was afraid he had lung(肺) cancer (癌). He seemed to see death was waiting for him. Tears(眼泪) ran down his face. He didn't see his wife was standing by him.

    “What's wrong with you, dear?” asked the woman.

    “Nothing,” the old man answered and covered his face with his hands.

    The old woman opened the book and understood at once. She said, “You must stop smoking right now.”

    “I began to smoke when I was nine, you know. How can't I do that?”

    “But I think health is more important.”

    Mr. King coughed again and his wife said, “Go to see a doctor tomorrow. He will be able to help you, I think.”

    The doctor told Mr. King to have an Xray examination(检查) of his lungs. And then he looked at the Xray carefully for a long time.

    “Tell me the truth, doctor.” said Mr.King, “Do you see any shadows(阴影)in my lungs?”

    “No, I don't see anything.”

    “Yes?” the old man said happily. “Really?”

    “Yes. Your lungs are turning black. How can I see any shadows?”

    I was walking down the street the other day when I suddenly saw a small purse lying on the ground. I picked it up and opened it to see if I could find the owner's name. There was nothing inside it except some money and an old photo of a woman and a young girl about twelve years old. The girl looked like the woman's daughter. I put the photo back and took the wallet to the police station. There I gave it to a policeman. Before I left, the policeman took down my name and address so that the owner could write to me and thank me if the policeman found the owner.

    That evening I went for dinner with my aunt and uncle. They also invited a young woman, so there were four people at the table. Her face seemed familiar. I was quite sure that we had met before, but I could not remember where I had seen her. During the talk, the young woman said that she had lost her purse that afternoon. At once I knew where I had seen her. She was just the young girl in the photo though she was now much older. She was very surprised, of course, when I was able to tell her what her purse was like.

    My uncle said that we should go to the police station at once to get the purse. As that policeman handed it over, he said it was an interesting coincidence(巧合). I not only found the purse, but also made friends with the person who had lost it.