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What measured how much lift the robot produced？
Play
Play is the principal business of childhood，and in recent years research has shown the great importance of play in the development of a human bein9．From earliest infancy． every child needs opportunity and the right materials for play，and the main tools of play are toys．Their main function is to suggest，encourage and assist play．To succeed in this they must be good toys，which children will play with often，and will come back to again and again．Therefore it is important to choose suitable toys for different stages of a child’S development．
In recent years research on infant development has shown that the standard a child is likely to reach，within the range of his inherited abilities，is largely determined in the first three years of his life．So a baby’S ability to profit from the right play materials should not be underestimated．A baby who is encouraged and stimulated，talked to and shown things and played with，has the best chance of growing up successfully．
In the next stage，from three to five years old，curiosity knows no bounds．Every type of suitable toy should be made available to the child。for trying out，experimenting and learnin9，for discovering his own particular ability．Bricks and jigsaws（七巧板）and construction toys；paintin9，scribbling（涂鸦）and making things；sand and water play； toys for imaginative and pretending play；the first social games for learning to play and get on with others．
By the third stage of play development——from five to seven or eight years——the child is at sch001．But for a few more years play is still the best way of learnin9，at home or at sch001．It is easier to see which type of toys the child most enjoys．
Until the age of seven or eight，play and work mean much the same to a child．But once reading has been mastered，then books and school become the main source of learnin9 Toys are still interesting and valuable，they lead on to new hobbies，but their significance has changed——to a child of nine or ten years，toys and games mean，as to adults．relaxation and fun．
第 41 题 The passage tells US that as a child grows up.
22 The United States of America is among the top 10 countries.
The best way to reduce your weight
You hear this：“No Wonder you are fat．An you ever do is eat．”You feel sad：“I skip my breakfast and supper.I run every morning and evening．What else can I do？”Basically you can do nothing．Your genes，not your life habits，determine your weight and your body constantly tries to maintain it．
Albert Stunkard of the University of Pennsylvania found from experiments that.“80 percent of the Children of two obese parents become obese，as compared with no more than 14 percent of the offspring of two parents of normal weight．”
How can obese people become normal or even thin through dieting？Well,dieting can be effective.but the health costs are tremendous．Jules Hirsch，a research physician at Rockefeller University,did a study of eight fat people．They were given a liquid formula providing 600 calories a dayl．After more than 10 weeks，the subjects lost 45kg on average．But after leaving the hospital．they au regained.The results were surprising：by metabolic measurement，fat people who lost large amounts ofweight seemed like they were starving．They had psychiatric problems．They dreamed of food or breaking their diet2．They were anxious and depressed；some were suicidal．They hid food in their rooms．Researchers warm that it is possible that weight reduction doesn’t result in normal weight，but in an abnormal state resembling that of starved non-obese people．
Thin people，however，suffer from the opposite：They have to make a great effort to gain weight．Ethan Sims，of the University of Vermont，got prisoners to volunteer to gain weight．In four to six months，they ate as much as they could．They succeeded in increasing their weight by 20 to 25 percent．But months after the study ended，they were back to normal weight and stayed there．
This did not mean that people are completely without hope in controlling their weight．It means that those who tend to be fat will have to constantly battle their genetic inheritance if they want to significantly lower their weight．
The findings also provide evidence for something scientists thought was true—each person has a comfortable weight range3．The range might be as much as 9kg．Someone might weigh 60—69kg without too much effort But going above of below the natural weight range is difficult．The body resists by feeling hungry or full and changing the metabolism to push the weight back to the range it seeks．
第 41 题 What determines your weight？
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