第4部分：阅读理解（第31～45题,每题3分,共45分）

下面有3篇短文,每篇短文后有5道题。请根据短文内容, 为每题确定1个最佳选项。

第一篇

The Hyper-X

The Hyper-X（超音速飞机）recently broke the record for air-breathingjet planes when it traveled at a Hypersonic speed（超音速）ofseven times the speed of sound. That's about 5,000 miles per hour. At thisspeed, you'd get around the world-flying along the equator（赤道）in less than 5 hours.

The Hyper-X is an unmanned, experimentalaircraft just 12 feet long. It achieves hypersonic speed using a special sortof engine known as a scramjet（超音速冲压式喷气发动机）.

For an engine to burn fuel andproduce energy, it needs oxygen. A jet engine, like those on passenger airplanesgets oxygen from the air. A rocket engine typically goes faster but has tocarry its own supply of oxygen. A scramjet engine goes as fast as a rocket, butit doesn't have to carry its own oxygen supply.

A scramjet's special design allowsit to obtain oxygen from the air that flows through the engine. And it does sowithout letting the fast-moving air put out the combustion（燃烧）flames. However, a scramjet engine worksproperly only at speeds greater than five times the speed of sound.

A booster rocket（助推火箭）carried the Hyper-X to an altitude of about100,000 feet for its test flight. The aircraft's record-beating flight lastedjust 11 seconds. That brief journey on March 27 makes a major milestone on theway to a new breed of very fast airplanes, says Weber J. A. Dam of theUniversity of Michigan in Ann Arbor. In the future, engineers predict, airplanesequipped with scramjet engines could transport cargo quickly and cheaply to thebank（边缘）of space. Such hypersonic jetscould carry passengers anywhere in the world in just a few hours.

Out of the three experimentalHyper-X aircrafts built for NASA, only one is now left The agency has plans foranother 11-second hypotonic flight, this time at 10 times the speed of sound.

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第二篇

Stop Eating Too Much

"Clean your plate!" and "Be amember of the clean-plate club!" Just about every kid in the US has heardthis from a parent or grandparent. Often, it's accompanied by an appeal: "Just thinkabout those starving orphans（孤儿）inAfrica!" Sure, we should be grateful for every bite of food. Unfortunately,many people in the UStake too many bites. Instead of staying "clean the plate", perhaps we shouldsave some food for tomorrow.

According to news reports, USrestaurants are partly to blame for the growing bellies （肚子）. A waiter puts a plate of food in front ofeach customer, with two to four times the amount recommended by the government,according to a USA Today story. Americans traditionally associate quantity withvalue and most restaurants try to give them that. They prefer to have customerscomplain about too much food rather than too little.

Barbara Rolls, a nutrition（营养）professor at Pennsylvania State University, toldUSA Today that restaurant portion sizes began to grow in the 1 970s, the sametime that the American waistline（腰围）beganto expand.

Health experts have tried to getmany restaurants to serve smaller portions. Now, apparently, some customers arecalling for this too. The restaurant industry trade magazine QSR reported lastmonth that 57 percent of more than 4,000 people surveyed believed restaurantsserved portions that were too large; 23 percent had no opinion; 20 percentdisagreed. But a closer look at the survey indicates that many Americans whocan't afford fine dining still prefer large portions. Seventy percent of thoseearning at least $150,000 per year prefer smaller portions; but only 45 percentof those earning less than $25,000 want smaller.

It's not that working classAmericans don't want to eat healthy. It's just that, after long hours atlow-paying jobs, getting less on their plate hardly seems like a good deal. Theylive from paycheck（薪金支票）to paycheck, happy to save alittle money for next year's Christmas presents.

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第三篇

Sunspots

It's not surprising that sunspots（太阳黑子）were observed by ancient astronomers（天文学家）. The largest sunspots on the sun can be seenwithout a telescope. It was not until the. invention of the telescope（望远镜）in the early 17th century, however, that systematicstudies of sunspots could be undertaken. The great astronomer Galileo was amongthe first to make telescopic observations of sunspots.

Sunspots are regions of extremelystrong magnetic fields（磁场）found on the sun's surface. Asunspot has a dark central core known as the umbra. The umbra is surrounded bya dark ring called the penumbra, where the magnetic field spreads outward. Sunspotsappear dark because they are giving off less radiation. They are cooler thanthe rest of the sun's Surface.

Sunspots are frequently observedin pairs or in paired groups. The members of a spot pair are identified as theleading spot and the following spot. They are identified by their position inthe pair in terms of the direction in which the sun rotates（旋转）.

The number of sunspots at any onetime varies. A large spot group may consist of as many as 10 groups and 300 Spotsacross the Sun. The number of spots changes in a fairly regular pattern calledthe sunspot cycle. The largest number occurs about every 11 years. At sunspotminimum, there are at most just a few small spots.

The average lifetime of anindividual spot group is roughly one solar rotation, which is about 25 days. Themost persistent large spots, however, can survive for two to three months

41.Careful observations and systematic studies of sunspots

　 A. were made by ancientastronomers.

　 B. started in the early17th century.

　 C. were made by Galileoonly.

　 D. could be made without atelescope.

42.Sunspots are cooler than the rest of the sun's surface because

　 A. they produce lessenergy.

　 B. they are buried in thesun.

　 C. they are far away frommagnetic fields.

　 D. they are close tomagnetic fields.

43. Theleading spot and the following spot are the names of

　 A. two large sunspots.

　 B. a large spot and a smallspot.

　 C. the two spots in a spotpair.

　 D. the central core and thering around it.

44. If anintense sunspot activity-had occurred in 1857, the next one would have been in

　 A. 1858.  B. 1862.  C. 1865.   D.1868.

45. Inthe last paragraph the word "persistent" means

　 A. important B. effective.  C. enduring.  D. visible.

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