four－wheel drive 意思是四轮驱动。（)

According to the way the machine operated, the felling machine can be classified into ______.

A. three-wheel machine vs. four-wheel machine

B. drive to tree machine vs. swing to tree machine

C. saw-head machine vs. shear-head machine

he farm and pretty much stayed in one place for their whole lifetime. One hundred years later, you learned to use some kind of technology at a factory, but this training and technology would also last your entire career. Once you made a decision about what job you wanted or could get, you keep that job the rest of your life and didn't have to think about it again. It was like getting on a train and knowing your exact destination.

In the late 20th century, as our job options increased, work was like getting a car and learning to drive. You could go to many more places than on the train, but still you could only go where there were roads.

These days, with so many opportunities and possibilities available, preparing for the future is like driving an all-terrain vehicle. With four-wheel drive, you don't have to stay on the road. In fact, some of the best places to go don't even have roads.

Two hundred years ago, people used to ______.

A．work on the farm and stay in a beautiful place

B．work on the farm and stay in the same place for most of time

C．work on the farm and just stay in the same place for a very short period of time

D．work on the farm and often change the place where they lived

drive shaft 意思是传动轴。()

he farm and pretty much stayed in one place for their whole lifetime. (19)One hundred years later, you learned to use some kind of technology at a factory, but this training and technology would also last your entire career. Once you made a decision about what job you wanted or could get, you keep that job the rest of your life and didn't have to think about it again. It was like getting on a train and knowing your exact destination.

In the late 20th century, as our job options increased, work was like getting a car and learning to drive. You could go to many more places than on the train, but still you could only go where there were roads.

These days, with so many opportunities and possibilities available, preparing for the future is like driving an all-terrain vehicle. With four-wheel drive, you don't have to stay on the road. In fact, some of the best places to go don't even have roads.

Two hundred years ago, people used to

A．work on the farm and stay in a beautiful place.

B．work on the farm and stay in the same place for most of time.

C．work on the farm and just stay in the same place for a very short period of time.

D．work on the farm and often change the place where they lived.

chines of a type never seen before.

It looks as if it came straight from the set of Star Wars. It has four-wheel drive and rises above rocky surfaces. It lowers and raises its nose when going up and down hills. And when it comes to a river, it turns amphibious: two hydrojets power it along by blasting water under its body. There is room for two passengers and a driver, who sit inside a glass bubble operating electronic, aircraft-type controls. A vehicle so daring on land and water needs windscreen wipers--but it doesn't have any. Water molecules are disintegrated on the screen's surface by ultrasonic sensors.

This unusual vehicle is the Racoon. It is an invention not of Hollywood but of Renault, a rather conservative French state-owned carmaker, better known for its family hatchbacks. Renault built the Racoon to explore new freedoms for designers and engineers created by advances in materials and manufacturing processes. Renault is thinking about startlingly different cars; other producers have radical new ideas for trains, boats and aeroplanes.

The first of the new freedoms is in design. Powerful computer-aided design (CAD) systems can replace with a click of a computer mouse hours of laborious work done on thousands of drawing boards. So new products, no matter how complicated, can be developed much faster. For the first time, Boeing will not have to build a giant replica of its new airliner, the 777, to make sure all the bits fit together. Its CAD sys- tem will take care of that.

But Renault is taking CAD further. It claims the Racoon is the world's first vehicle to be designed within the digitized world of virtual reality. Complex programs were used to imitate the vehicle and the land that it was expected to cross. This allowed a team led by Patrick Le Qucment, Renault's industrial-design director, to "drive" it long before a prototype existed.

Renault is not alone in thinking that virtual reality will transform. automotive de- sign. In Detroit, Ford is also investigating its potential. Jack Telnac, the firm's bead of design, would like designers in different parts of the world to work more closely together, linked by computers. They would do more than style. cares. Virtual reality will allow engineers to peer inside the working parts of a vehicle. Designers will watch bearings move, oil flow, gears mesh and hydraulics pump. As these techniques catch on, even stranger vehicles are likely to come along.

Transforming these creations from virtual reality to actual reality will also become easier, especially with advances in materials. Firms that once bashed everything out of steel now find that new alloys of composite materials (which can be made from mixtures of plastic, resin, ceramics and metals, reinforced with fibers such as glass of carbon) are changing the rules of manufacturing. At the same time, old materials keep getting better, as their producers try to secure their place in the factory of the future. This competition is increasing the pace of development of all materials.

With composites, it is possible to build many different parts into a single component. Fiat, Italy's biggest car maker has worked out that it could reduce the number of components needed in one of its car bodies from 150 to 16 by using a composite shell rather than one made of steel. Aircraft and cars may increasingly be assembled as if they were plastic kits.

How does the Racoon cross water？

A．It swims,

B．It raises its nose.

C．It uses hydrojets.

D．It uses its four-wheel drive.

es a bove rocky surfaces. It lowers and raises its nose when going Up and down hills. And when it comes to a river, it turns amphibious; two hydro jets power it along by blasting water under its body. There is room for two passengers and a driver, who sit inside a glass bubble operating electronic, aircraft-type controls. A vehicle so daring on land and water needs windscreen wipers -- but it doesn't have any. Water molecules are disintegrated on the screen's surface by ultrasonic sensors.

This unusual vehicle is the Racoon. It is an invention not of Hollywood but of Renault, a rather conservative French state-owned carmaker, better known for its family hatchbacks. Renault built the Racoon to explore new freedoms for designers and engineers created by advances in materials and manufacturing processes. Renault is thinking about startlingly different cars; other producers have radical new ideas for trains, boats and aeroplanes.

The first of the new freedoms is in design. Powerful computer-aided design (CAD) systems can replace with a click of a computer mouse hours of laborious work done on thousands of drawing boards. So new products, no matter how complicated, can be developed much faster. For the first time, Boeing will not have to build a giant replica of its new airliner, the 777, to make sure all the bits fit together. Its CAD system will take care of that.

But Renault is taking CAD further. It claims the Racoon is the world's first vehicle to be designed within the digitised world of virtual reality. Complex programs were used to simulate the vehicle and the terrain that it was expected to cross. This allowed a team led by Patrick Le Quement, Renault's industrial-design director, to "drive" it long before a prototype existed.

Renault is not alone in thinking that virtual reality will transform. automotive design. In Detroit, Ford is also investigating its potential. Jack Telnac, the firm's head of design, would like designers in different parts of the world to work more closely together, linked by computers. They would do more than style. cars. Virtual reality will allow engineers to peer inside the working parts of a vehicle. Designers will watch bearings move, oil flow, gears mesh and hydraulics pump. As these techniques catch on, even stranger vehicles are likely to come along.

Transforming these creations from virtual reality to actual reality will also become easier, especially with advances in materials. Firms that once bashed everything out of steel now find that new alloys or composite materials (which can be made from mixtures of plastic, resin, ceramics and metals, reinforced with fibers such as glass or carbon) are changing the rules of manufacturing. At the same time, old materials keep getting better, as their producers try to secure their place in the factory of the future. This competition is increasing the pace of development of all materials.

One company in this field scaled composites. It was started in 1982 by Burt Rutan, an aviator who has devised many unusual aircraft. His company develops and tests prototypes that have ranged from business aircraft to air racers. It has also worked on composite sails for the America's Cup yacht race and on General Motors' Ultralite, a 100-miles-per-gallon experimental family car built from carbon fiber.

Again, the Racoon reflects this race between the old and the new. It uses conventional steel and what Renault describes as a new "high-limit elastic steel" in its chassis. This steel is 30% lighter than the usual kind. The Racoon also has parts made from compostites. Renault plans to replace the petrol engine with a small gas turbine, which could be made from heat-resisting ceramics, and use it to run a generator that would provide power for electric motors at each wheel.

With composites it is possibl

A．It swims.

B．It raises its nose.

C．It uses hydrojets.

D．It uses its four-wheel drive.