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资料：Directions : There is 1 passage in this part. The passage is followed by some questions or unfinished statements. For each of them there are four choices , You should decide on the best choice.

Your face is the future of smartphone security. Apple made that clear last week when it unveiled the pricey iPhone X. Apple claims to have conquered many of the challenges that have prevented the widespread use offacial biometrics. But a number of computer-vision researchers say they are skeptical that a smartphone-based system like FaceID can account for things like variable lighting conditions or subtle changes in a person's appearance to create a secure-yet-practical way to unlock a phone a dozen or more times a day.

Apple’s new technology does sound promising. The company says FaceID creates a “precise depth map” of one’s visage by projecting more than 30,000 infrared dots against a person’s face, then using the phone’s infrared TrueDepth camera and high-power microchip to collect and analyze the results. Users are also asked to turn their head as they scan so the phone's machine-learning algorithm can measure the face from several angles and create a more detailed 3-D map of their features. Once the map is created and stored, the iPhone X uses infrared light to help FaceID scan a person’s face even in the dark. Meanwhile, machine-learning algorithms running on the phonekeep track of changes in a person's appearance—including glasses, facial hair and hats—so the smartphone’s accuracy improves over time.

Despite advances in facial recognition in recent years, it remains unclear whether FaceID will work in a variety of conditions while also keeping the iPhone X secure. Hackers, for example, quickly found a way to bypass the Samsung Galaxy S8's facial-recognition scanner when it was introduced in March: They tricked the device by simply showing it a photo of the user. FaceID’s use of 3-D facial maps could address that problem. But historically it has been a big challenge for such a system to recognize faces under different lighting conditions and from a variety of angles.

Apple showed off FaceID last week under relatively controlled conditions, says Arun Ross, a professor of computer science and engineering at Michigan State University. "Clearly the demo was very interesting," he says. "But at the same time some extraordinary claims were made." Apple' s Schiller said, for example, that the chance a random person' s face could unlock someone else' s iPhone X was one in a million——much more secure than TouchID. Ross says, however, that it is not clear how often FaceID fails to recognize its owner. When contacted, Apple declined to elaborate on Schiller' s comments.

“Like all biometrics, FaceID will have a problem with revocation,” says Vitaly Shmatikov, a computer science professor at Cornell Tech. “If a password is compromised, it can be changed—but a face cannot be changed.” Apple touts its ability to secure data on its iPhones, which do not share biometric information with the company’s servers. Still, Ross says, hackers always seem to find a way around even the tightest security.

What is the computer-vision researchers’ main concern of iPhone X’ s FaceID?

A.They have concerns of the security and convenience of FaceID
B.They don’ t believe iPhone X’ s FaceID can successfully unlock a phone every time
C.They have doubts of its technique to overcome variable lighting and subtle change of the user’s face
D.They are mainly worried about the smartphone’ s accuracy

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答案： B

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本题考查的是细节理解。

【关键词】computer-vision researchers ’main concern

【主题句】第1自然段But a number of computer-vision researchers say they are skeptical that a smartphone-based system like FaceID can account for things like variable lighting conditions or subtle changes in a person’s appearance to create a secure-yet-practical way to unlock a phone a dozen or more times a day. “但是很多计算机研究员说，他们怀疑像FaceID这种基于智能手机的系统，是否能在诸如灯光变化或人脸部发生细微变化的情况下还能安全又实用，一天之内解锁十几次或更多次。”

【解析】题目意为：“设计iPhone X面部识别功能的视觉研究员最关心什么”。选项A意为“他们担忧面部识别的安全和便捷问题”；选项B意为“他们不相信iPhone X的面部识别能够每次成功解锁手机”；选项C意为“他们怀疑这项技术是否能够克服灯光及人脸的微弱变化”；选项D意为“他们主要担心智能手机的准确性”。根据主题句可知这些研究人员担心的是iPhone X的FaceID不能多次解锁，故答案选B；C选项对应的variable lighting and subtle change of the user’s face在主题句中只是科研人员举例的无法解锁的一些情况，并非核心问题，所以C选项不正确。