单选题
Mr. Smith was and he went to see a (41) .The doctor asked him to put out his tongue, and then he said, "OK, You can put your tongue back now. There's nothing wrong with you, but I'm (42) you have a problem. You (43) ever take exercise. " "But, doctor," Mr. Smith said, "I don't think so. " "Don't tell me what you think," the doctor said, "1 know what you need. I see a lot of people like you. None of them goes any exercise. They sit in offices all day and (44) the television in the evening. You must walk quickly for at least 20 minutes a day. " "1 don't want to hear any excuse(借口) ," the doctor said. "You must find time for exercise. If you don't, you will get fat and have (45) problems. " "But I walk every day," Mr. Smith said. "Oh, yes, and I know what kind of walking that is. You walk a few meters to the bus stop from your house, a few more meters from the bus stop to your office, and a few more meters from your office to your dining-room for lunch and back. That's not a real walk. I'm talking about a walk in the park or by the lake for twenty (46) every day. " "Would you please (47) me, doctor?" Mr. Smith said, getting (48) angry with his doctor. "I'm a (49) ," Mr. Smith went on, "and I walk for nearly seven hours every day. " For a moment the doctor was silent, then he said quietly, " Put out your (50) again, will you?/