未分类题

Computer Mouse
The basic computer mouse is an amazingly clever invention with a relatively simple design that allows us to point at things on the computer and it is very productivE.Think of all the things you can do with a mouse like selecting text for copying and pasting, drawing, and even scrolling on the page with the newer mice with the wheel. Most of us use the computer mouse daily without stopping to think how it works until it gets dirty and we have to learn how to clean it. We learn to point at thing before we learn to speak, so the mouse is a very natural pointing devicE.Other computer pointing devices include light pens, graphics tablets and touch screen, but the mouse is still our workhorsE.
The computer mouse was invented in 1964 by Douglas Englehart of Stanford University. As computer screens became popular and arrow keys were used to more around a body of text, it became clear that a pointing device that allowed easier motion through the text and even selection of text would be very useful. The introduction of the mouse, with the Apple Lisa computer in 1983, really started the computer public on the road to relying on the mouse for routine computer tasks.
How does the mouse work? We have to start at the bottom, so think upside down for now. It all starts with mouse ball. As the mouse ball in the bottom of the mouse rolls over the mouse pad, it presses against and turns two shafts. The shafts are connected to wheels with several small holes in them. The wheels have a pair of small electronic light-emitting devices called light emitting diodes (LED) mounted on either sidE.One LED sends a light beam to the LED on the other sidE.As the wheels spin and a hole rotates by, the light beam gets through to the LED on the other sidE.But a moment later the light beam is blocked until the next hole is in placE.The LED detects a changing pattern of light, converts the pattern into an electronic signal, and sends the signal to the computer through wires in a cable that goes out the mouse body. This cable is the tail that helps give the mouse its namE.The computer interprets the signal to tell it where to position the cursor on the computer screen.
So far we have only discussed the basic computer mouse that most of you probably have or have useD.One problem with this design is that the mouse gets dirty as the ball rolls over the surface and picks up the dirt. Eventually you have to clean your mousE.The newer optical mice avoid this problem by having no moving parts.
Most computer users want to know how the computer mouse works.
A.Right
B.Wrong
C.Not mentioned

A.B.
C.
D.
Most
E.
A.Right
B.Wrong
C.Not

【参考答案】

B
解析:原文第一段第三句表明大多数人虽然每天都在用鼠标但并没有停下来去思考鼠标的工作原理。
热门 试题

未分类题
'Hidden' Species May Be Surprisingly CommonCryptic(隐蔽的;隐藏的)species -- animals that appear identical but are genetically quite distant --may be much more widespread than previously thought. The findings could have major implications in areas ranging from biodiversity(生物多样性)estimates and wildlife management, to our understanding of infectious diseases and evolution.Reports of cryptic species have increased dramatically over the past two decades with the advent of relatively inexpensive DNA (脱氧核糖核酸) sequencing technology. Markus Pfenninger and Klaus Schwenk, of the Goethe-Universitat in Frankfurt, Germany, analyzed all known data on cryptic animal species and discovered that they are found in equal proportions throughout all major branches of the animal kingdom and occur in equal numbers in all biogeographical(生物地理学的)regions.Scientists had previously speculated that cryptic species were predominantly found in insects and reptiles(爬行动物), and were more likely to occur in tropical rather than temperate(温带的)regions. 'Species that are seemingly widespread and abundant could in reality be many different Cryptic species that have low populations and are highly endangered,' says Pfenninger. Until the genetic information of all species in at least one taxon(分类单元)is thoroughly studied, no one will know just how many cryptic species exist, 'It could be as high as 30%,' Pfenninger says.'I'm extremely surprised by their results, ' says Alex Smith of the University of Guelph in Ontario, CanadA.'It's a call to arms to keep doing the broad kind of genetic studies that we are doing. 'Sampling as many individuals as possible, scientists hope to complete work on all fish and birds in another 5 to 10 years. Once either of these taxonomic groups is completed, Pfenninger says researchers will be able to decide how many cryptic species exist throughout the animal kingdom.Examples of cryptic species include the African elephant. A 2001 study found the elephants were actually two genetically distinct, non-interbreeding (非杂交繁殖的) species, the African bush elephant and the African elephant. The species are currently listed as vulnerable and threatened, respectively, by the World Conservation Union (WCU).The reclassifications are more than an academic exercisE.They define populations that have evolved independently of each other and whose genetic differences can have significant consequences.In the early 1900s misidentification of mosquito species based on morphology confused: attempts to control malaria(疟疾)in EuropE.Ultimately, what was thought to be a single species was actually made up of six sibling(同胞,同属)species, only three of which transmitted the diseasE.' The basic unit in biology is always the species, and you have to know what you are dealing with,' Pfenninger says. Much previous research is now no longer used, he says, because it is not clear what species was being studieD.Which of the following about the significance of the research on cryptic species is NOT true?A.The results of the research can help the development of many other research areas.B.The results of the research can help the development of biodiversity estimates.C.The results of the research can help our understanding of infectious disease evolution.D.The results of the research can help our understanding of 'survival of the fittest'.
A.B.
C.
D.
E.
F.
G.'
H.
Which
I.The
J.
B.The
K.
C.The
L.
D.The