Mr. Brown is 70 years old. One day he went to see his1. He said he had an ache 2his left leg. The doctor looked over（检查）his leg but didn't 3 anything wrong. So he 4 the old man a physical examination（体检）. Then he thought he knew the answer.

The doctor gave Mr. Brown some 5 and said, "I'm sorry. The ache in your leg is caused (被引起) by old age. There is 6I can do about it. I hope this medicine can make you feel better.”

The old man was very7 to hear that. He cried, "That's impossible!"

The doctor said, "What? Why do you think so?” The old man answered, "I'm not a doctor, 8I know you are wrong. My right leg9fine. "

"So what?" asked the doctor. "What 10 does that make?"

"Well, they are of the SAME AGE!"