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The use of new building materials and the introduction of such new technologies as the elevator and the air-conditioner have played an important role_____
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Why is the Native Language Learnt So Well
How does it happen that children learn their mother tongue so well7 When we compare them with adults learning a foreign language，we often find this interesting fact．A little child without knowledge or experience often succeeds in a complete mastery of the language．A grown-up person with fully developed mental powers，in most cases，may end up with a faulty and inexact command．What accounts for this difference
Despite other explanations the real answer in my opinion lies partly in the child himself，partly in the behavior. of the people around him．In the first place，the time of learning the mother tongue is the most favorable of all，namely the first years of life．A child hears it spoken from morning till night and，what is more important，always in its genuine form，With the right pronunciation，fight intonation，right use of words and right structure．He drinks in all the words arid expressions which come to him in a fresh，ever-bubbling spring．There is no resistance：there is perfect assimilation(吸收)．
Then the child has，as it were，private lessons all the year round，while an adult language-student has each week a、limited number of hours which they generally share with others．The child has another advantage：he hears the language in all possible situations。 always accompanied by the right kind of gestures and facial expressions．Here there is nothing unnatural，such as is often found in language lessons in schools，when one talks about ice and snow in June or scorching(灼热的)heat in January．And what a child hears is generally what immediately interests him. Again and again, when his attempts at speech are successful his desires are understood and fulfilled.
Finally though a child's "teachers" may not have been trained in language teaching, their relations with him are always close and personal. They take great pains to make their lessons easy.
第 20 题 Compared with adults learning a foreign language, children learn their native language with ease.
If not for the English examination I would have gone to the concert last Sunday,
Why do people's eyes read by little "jumps"？
A Pool Watch
Swimmers can drown in busy swimming pools when lifeguards fail to notice that they are in trouble．The Royal Society for the Prevention of Accidents says that on average 15 people are drown in British pools each year, but many more suffer major injury after getting into difficulties．Now a French company has developed an artificial intelligence system called Poseidon that sounds the alarm when it sees someone in danger of drowning．
When a swimmer sinks towards the bottom of the pool, the new system ．sends an alarm signal to a poolside monitoring station and a lifeguard's pager．In trials at a pool in Ancenis, near Nantes, it saved a life within just a few months, says Alistair McQuade, a spokesman for its maker, Poseidon Technologies．
Poseidon keeps watch through a network of underwater and overhead video cameras．AI software analyses the images to work out swimmers' trajectories(轨迹)．To do this reliably, it has to tell the difference between a swimmer and the shadow of someone being cast onto the bottom or side of the pool．"The underwater environment is a very dynamic one with many shadows and reflections dancing around," says McQuade．
The software does this by "projecting" a shape in its field of view onto an image of the far wall of the pool．It does the same with an image from another camera viewing the shape from a different angle．If the two projections are in the same position, the shape is identified as a shadow and is ignored．But if they are different, the shape is a swimmer and sothe system follows its trajectory．
To pick out potential drowning victims, anyone in the water who starts to descend slowly is added to the software's "pre-alert" (预警) list, says McQuade．Swimmers who then stay immobile on the pool bottom for 5 seconds or more are considered in danger of drowning．Poseidon double-checks that the image really is of a swimmer, not a shadow,by seeing whether it obscures the pool's floor texture when viewed from overhead．If so,it alerts the lifeguard, showing the swimmer' s location on a poolside screen．
The first full-scale Poseidon system will be officially opened next week at a pool in High Wycombe, Buckinghamshire．One man who is impressed with the idea is Travor Bavlis, inventor of the clockwork radio．Baylis runs a company that installs swimming pools and he was once an underwater escapologist with a circus．"I say full marks to them if this works and can save lives," he says．But he adds that any local authority spending 30,000-plus pounds on a Poseidon system ought to be investing similar amounts in teaching children to swim．
第 36 题 AI means the same as____．
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