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D. enjoy walking more 3. From the passage we know that ______. A. mice need to eat more and exercise more B. children need more exercise than other people C. old people like to take medicine to treat their illness D. middleaged people are easy to get fat 4. The bones of old people are easy to break because_______. A. there is less calcium in their bones than in those of other people B. they are easy to bee ill C. they eat less than other people D. they have less exercise than other people 答案: 1. C 2. A 3. D 4. A