专题限时检测(二十一)阅读理解C篇专练(二)(共3篇，限时24分钟)A(2019南京、盐城二模)Listen carefully to the footsteps in the family home, especially if it has wooden floors, and you can probably work out who it is that is walking about.The features most commonly used to identify people are faces, voices, finger prints and retinal scans.But their “behavioural biometrics”， such as the way they walk, are also giveaways.Researchers have, for several years, used video cameras and computers to analyse peoples gaits, and are now quite good at it.But translating such knowledge into a practical identification system can be tricky especially if that system is supposed to be hidden.Cameras are often visible, are hard to set up, require good lighting and may have their view blocked by other people.So a team led by Krikor Ozanyan of the University of Manchester, in England and Patricia Scully of the National University of Ireland, in Galway have been looking for a better way to recognise gait.Their answer: pressuresensitive mats.In themselves, such mats are nothing new.They have been part of security systems for donkeys years.But Dr Ozanyan and Dr Scully use a complex version that can record the amount of pressure applied in different places as someone walks across it.These measurements form a pattern unique to the walker.Dr Ozanyan and Dr Scully therefore turned, as is now common for anything to do with pattern recognition, to an Artificial Intelligence system that uses machine learning to recognise such patterns.It seems to work.In a study published earlier this year the two researchers tested their system on a database of footsteps trodden by 127 different people.They found that its error rate in identifying who was who was a mere 0.7%.And Dr Scully says that even without a database of footsteps to work with the system can determine someones sex women and men, with wide and narrow pelvises (骨盆) respectively, walk in different ways and guess, with reasonable accuracy, a subjects age.A matbased gaitrecognition system has the advantage that it would work in any lighting conditions even pitchdarkness.And though it might fail to identify someone if, say, she was wearing stilettos and had been entered into the database while wearing trainers, it would be very hard to fool it by imitating the gait of an individual who was allowed admission to a particular place.The latest phase of Dr Ozanyans and Dr Scullys project is a redesign of the mat.The old mats contained individual pressure sensors.The new ones contain optical fibres(光纤)Lightemitting diodes (二极管) distributed along two neighbouring edges of a mat transmit light into the fibres.Sensors on the opposite edges (and thus the opposite ends of the optical fibres) measure how much of that light is received.Any pressure applied to part of the mat causes a distortion (变形) in the fibres and a consequent change in the amount of light transmitted.Both the location and amount of change can be plotted and analyzed by the machinelearning system.Dr.Ozanyan says that the team have built a demonstration fibreoptic mat, two meters long and a metre wide, using materials that cost 100(130)They are now talking to companies about commercializing it.One application might be in health care, particularly for the elderly.A fibreoptic mat installed in a nursing home or an old persons own residence could monitor changes in an individuals gait that warn certain illnesses.That would provide early warning of someone being at greater risk of falling over, say, or of their cognition becoming damaged.Gait analysis might also be used as a security measure in the workplace, monitoring access to restricted areas, such as parts of military bases, server farms or laboratories dealing with harmful materials.In these cases, employees would need to agree to their gaits being scanned, just as they would agree to the scanning of their faces or retinas for optical security systems.Perhaps the most fascinating use of gaitrecognition mats, though, would be in public places, such as airports.For that to work, the footsteps of those to be recognised would need to have been stored in a database, which would be harder to arrange than the collection of mugshots and fingerprints that existing airport security systems rely on.Some people, however, might volunteer for it.Many aircrew or preregistered frequent flyers would welcome anything that speeded up one of the most tiresome parts of modern travel.语篇解读：本文主要介绍了一种新的识别方法：步态识别。1Camerabased gait recognition fails to come into wide use, because _.aits not easy to find the camerasbfinger print recognition is still popularcsometimes the cameras can be covereddits a waste of money to fix the equipmentegood lighting conditions cant be guaranteedfits difficult to set up the systemAa、c、fBb、d、eCc、d、f Dc、e、f解析：选D细节理解题。根据第二段的一开始的三句话可知，虽然人们已经很擅长利用摄像机和计算机来分析人们的步态，但是将这些知识转化为实际的识别系统可能很难。主要有这样几个原因：cameras are hard to