The silk produced in Hangzhou feels extremely .

A、The ant silkworm.

B、The moth.

C、The adult silkworm.

D、The pupa.

A.soft

B. softly

C. softness

D. Softy

A．The ant silkworm．

B．The moth．

C．The adult silkworm．

D．The pupA．

根据以下材料，回答题

New Understanding of Natural Silk"s Mysteries

Natural silk， as we all know， has a strength that manmade materials have long struggled to match. In a discovery that sounds more like an ancient Chinese proverb than a materials science breakthrough， MIT researchers have discovered that silk gets its strength from its weakness. Or，more specifically， its many weaknesses. Silk gets its extraordinary durability and ductility from an unusual arrangement of hydrogen bonds that are inherently very weak but that work together to create a strong， flexible structure.

Most materials- especially the ones we engineer for strength- get their toughness from brittleness. As such， natural silks like those produced by spiders have long fascinated both biologists and engineers because of their light weight， ductility and high strength （pound for pound， silk is stronger than steel and far less brittle）. But on its face， it doesn"t seem that silks should be as strong as they are; molecularly， they are held together by hydrogen bonds， which are far weaker than the covalent bonds found in other molecules.

To get a better understanding of how silk manages to produce such strength through such weak bonds， the MIT team created a set of computer models that allowed them to observe the way silk behaves at the atomic level. They found that the arrangement of the tiny silk nanocrystals is such that the hydrogen bonds are able to work cooperatively， reinforcing one another against extemal forces and failing slowly when they do fail， so as not so allow a sudden fracture to spread across a silk structure.

The result is natural silks that can stretch and bend while retaining a high degree of strength.

But while that"s all well and good for spiders， bees and the like， this understandingof silk geometry could lead to new materials that are stronger and more ductile than those we can currently manufacture. Our best and strongest materials are generally expensive and difficult to produce （requiring high temperature treatments or energy-intensive processes）.

By looking to silk as a model， researchers could potentially devise new manufacturing methods that rely on inexpensive materials and weak bonds to create less rigid， more forgiving materials that are nonetheless stronger than anything currently on offer. And if you thought you were going to get out of this materials science story without hearing about carbon nanotubes， think again. The MIT team is already in the lab looking into ways of synthesizing silk-like structures out of materials that are stronger than natural silk—— like carbon nanotubes. Super-silks are on the horizon.

MIT researchers carry out the study to illustrate an ancient Chinese proverb. 查看材料

A.Right

B.Wrong

C.Not mentioned

听力原文： When cars first started appearing on the streets of the world, few people took them seriously. They were toys--playthings for grown men who didn't have much to do. No one thought that the automobile would become the world's most popular means of transportation.

When Henry Ford started selling his Model T in 1908, he changed all that. Ford believed that a car should be low-cost transportation that everyone could afford. So he decided to make such a car. First, he wanted a dependable automobile that wouldn't break down easily. Then he wanted a simple engine that almost anyone could fix.

Ford wanted to sell the car at a low price, so he had to make it at a low cost. Thus he made only one model and designed one color--black.

In 1932, the Duesenberg brothers produced a car that many people think it was the most luxurious automobile ever made--the Duesenberg SJ. Every Duesenberg car was custom-made, so each one was different. But it usually weighed about 7,000 pounds and had a very wide wheelbase--150 inches. It also had a 400 horsepower engine that could drive the huge car from zero to 100 miles per hour in 17 seconds.

The inside was very luxurious, too. It had the best silk, leather, silver and wood. A Dusenberg car was definitely expensive but rich people often felt that they had to own one. Unfortunately, the car cost so much to produce that the company lost money. In 1937, after making only 500 of them, the Duesenbergs stopped producing this kind of cars forever.

(33)

A．The two models of cars.

B．The history of car industry.

C．The development of cars in America.

D．The structure of Duesenberg cars.

A.

B.

C.

D.