One day, a young man goes to see a doctor. The man looks strong but tired. He says he can't sleep well every night. He is very worried. The doctor examines(检查) him carefully. But there is nothing wrong with him. The doctor says, "Don't worry. You can count from one to ten again and again. Keep doing that until you fall asleep."
After a few days, the young man comes to see the doctor again. He looks a little angry. "Doctor, it doesn't work." he says, "I count every night. But every time when I count to eight, I jump from the bed."
"But why?" the doctor asks.
The young man answers, "I am a boxer.
B . 
C . 
