The Sahara The name Sahara derives from the Arabic word for “desert“ or “steppe“. At 3.5 million square miles, an area roughly the size of the United States, the Sahara Desert in northern Africa is the largest desert in the world. It spans the continent from the Atlantic Ocean to the Red Sea. Daytime temperatures can reach as high as 130°F. The humidity sometimes gets into the teens. But it can also be as low as 2. 5 percent, the lowest in the world. Most of the Sahara receives less than five inches of rain per year, while large areas sometimes have no rainfall at all for years. At the heart of the Sahara is the landlocked north African country of Niger. Here the sand dunes can be 100 feet tall and several miles long. Here sand plains stretch over an area larger than Germany where there is neither water nor towns. Yet sitting in the midst of the surrounding desert is the town of Bilma. Suddenly there are pools of clear water. Surprisingly, there are groves of date palms. Underground water resources, or oases, sufficient to support irrigated agriculture are found in dry stream beds and depressions. Irrigation ditches run off a creek to water fields. Corn, cassava, tea, peanuts, hot peppers, and orange, lime , and grapefruit trees grow in these fields. Donkeys and goats graze on green grass. The Sahara of Niger is still a region where you can see a camel caravan of 500 camels tied together in loose lines as long as a mile, traveling toward such oasis towns. There a caravan will collect life-sustaining salt, which is mined from watery basins, and transport it up to 400 miles back to settlements on the edges of the desert. The round trip across the vast sands takes one month.

The discovery was sensational. sexy surf)rising exceptional exciting

Soil is the surface layer of the Earth that nourishes and supports the growth of rooted plants. accepts arranges feeds shelters

The eternal motion of the stars fascinated him. long never-ending boring extensive

The book made a great impact on its readers. force influence surprise power

A. electromagnetic energy B. electromagnetic energy travels through space C. came from the sun D. when a change in the nucleus of an atom takes place E. when the sunrays are fierce F. chemical energy is generated

GPS Child Locator Lets Parents Know Their Whereabouts Children may not like it but a British technology firm has invented an electronic babysitter—a wristwatch-like device that lets parents know where their children are at all times. The GPS Child Locator attaches firmly to a child ’ s wrist and contains a Global Positioning System(GPS), said Matthew Salmon, a spokesman for the manufacturer.【B1】______“It tracks your child. “ “ It only starts working when the device is connected to the child’ s wrist, “ Salmon said, “ and is very difficult to get off. “【B2】______“It would give you a Google Maps image with their exact location, the street name and the zip code. “ When a child is wearing the device, a parent sends the text message “where are you“ and the child’ s current location is sent back to a mobile phone or computer.【B3】______ “ You can also set up a perimeter(界限), an invisible fence, and if they wander out of this invisible fence which you put on the Internet it will warn you, “ Salmon said.【B4】______ Salmon said the device is waterproof and shockproof and lasts for three days with a full charge. It will be available in both Britain and the United States this year and retails for 200 dollars with a 10 dollar a month subscription(订阅)fee. He said the company had received thousands of inquiries about the device since launching it this week. “Fifty percent are positive, 50 percent are negative, that it’ s a bit Big Brotherish(干涉人身自由的), “ he said.【B5】______ A. “It will text you immediately. B. Double fixing devices easy to handle. C. Parents can also log on to the company website to discover their child’ s present location. D. “ It uses GPS and GSM(Global System for Mobiles)technology with an accuracy of 10 feet(three meters), “ he said. E. “But it’ s really just about letting you have freedom of mind. F. “Even if the child managed to get it off it would send an emergency text message through to your mobile phone, “ he said.

Gas does accumulate in the mines around here. increase spread collect grow

When Jack eventually overtook the last truck, he pulled over to the inside lane. skipped passed reached led

We need to extract the relevant financial data. store save obtain review

Electromagnetic Energy 1 White light seems to be a combination of all colors. The energy that comes from a source of light is not limited to the kind of energy you can see. Heat is given off by a flame or an electric light. On a cloudy day it is possible to get a sunburn even though you feel cool. Visible light and the kind of energy that produce warmth and sunburn are examples of electromagnetic energy. 2 The sun is 93 million miles away from the earth. Yet we can use energy from the sun because electromagnetic energy travels through space. 3 Many other kinds of energy are also types of electromagnetic energy. Radio, television, and radar signals travel from transmitters to receivers as low-energy electromagnetic waves. Infrared(红外线的)radiation is an electromagnetic wave. When it is absorbed by matter, heat is produced. Waves of infrared and visible light have more energy than waves of radio, television, or radar. Ultraviolet rays(紫外线)and X-rays are electromagnetic waves with even greater amounts of energy. Infrared radiation is used in cooking food and heating buildings. Sunlight and electric lights are part of our requirements for normal living. Ultraviolet radiation is useful in killing certain disease organisms. X-rays and gamma rays have so much energy that they travel right through solid objects. They can be used to detect and treat cancer. X-rays are used in industry to find hidden cracks in metal, and in medicine to reveal broken bones. 4 Usually we use electricity to generate electromagnetic energy. The source of most of our energy is the sun. Heat from the sun causes water to evaporate. When the water falls to the earth as rain, some of it is trapped behind dams and then used to operate electric generators. Other generators are powered by coal, but the energy stored in coal came from the sun, too. 5 Until recently, the source of the tremendous amount of energy given off by the sun was a puzzle. If the sun depended on chemical reactions, it would have used up all its energy long ago. Experiments with electromagnetic radiation led to the theory that mass can be converted into energy. About forty years after the theory was proposed, nuclear energy was harnessed(利用)by man. Chemical energy comes from electron(电子)rearrangement. Nuclear energy comes from a change in the nucleus of an atom. Compared with chemical reactions, nuclear reactions release millions of times more energy per pound of fuel. We now believe that the sun’ s energy comes from the nuclear reactions in which hydrogen is changed into helium(氦). 6 Nuclear energy is beginning to compete with coal as an economical source of power to generate electricity. It is also being used to operate engines in large ships. Scientists continue to seek new and better methods of obtaining and using energy. A. Nuclear Reactions as the Lasting Source of the Sun’ s Energy B. The Most Important Source of Energy C. Types of Electromagnetic Energy D. X-rays Are Used to Detect and Treat Cancer E. Seeking New Sources of Energy F. Nuclear Energy Is Beginning to Compete With Coal

When she was invited to the party, she readily accepted. willingly suddenly firmly quickly

Their translation was faulty. wrong ambiguous unclear unbelievable

There is an abundant supply of cheap labor in this country. a steady a plentiful an extra a meager

The train came to an abrupt stop, making us wonder where we were. slow noisy sudden jumpy

Certain programs work better for some than for others. Your doctor will be able to tell you which option is best suited for you. alternative alternation detection diagnosis

At first Mr. Harrison lost money on his investment, but finally it paid off. borrowed money survived was wealthy succeeded

In the darkness, the hunter perceived that something was moving in the bushes. discovered realized saw sensed

They all think that the prices of personal computers will soon plunge. fall leap rise sink

EL Nino While some forecasting methods had limited success predicting the 1997 EL Nino(厄尔尼诺现象，指赤道东太平洋南美沿岸海水温度剧烈上升的现象)a few months in advance, the Columbia University researchers say their method can predict large EL Nino events up to two years in advance. That would be good news for governments, farmers and others seeking to plan for the droughts and heavy rainfall that EL Nino can produce in various parts of the world. Using a computer, the researchers matched sea-surface temperatures to later EL Nino occurrences(发生)between 1980 and 2000 and were then able to anticipate EL Nino events dating back to 1857, using prior sea-surface temperatures. The results were reported in the latest issue of the journal Nature. The researchers say their method is not perfect, but Bryan C. Weare, a meteorologist(气象学家)at the University of California, Davis, who was not involved in the work, said it “ suggests EL Nino is indeed predictable“. “This will probably convince others to search around more for even better methods, “ said Weare. He added that the new method “ makes it possible to predict EL Nino at long lead(提前的)times“. Other models also use sea-surface temperatures, but they have not looked as far back because they need other data, which is only available for recent decades, Weare said. The ability to predict the warming and cooling of the Pacific is of immense importance. The 1997 EL Nino, for example, caused an estimated $20 billion in damage worldwide, offset(抵消)by beneficial effects in other areas, said David Anderson, of the European Centre for Medium-Range Weather Forecasts in Reading, England. The 1877 EL Nino, meanwhile, coincided(同时发生)with a failure of the Indian monsoon and a famine that killed perhaps 40 million in India and China, prompting the development of seasonal forecasting, Anderson said. When EL Nino hit in 1991 and 1997, 200 million people were affected by flooding in China alone, according to a 2002 United Nations report. While predicting smaller EL Nino events remains tricky(复杂的), the ability to predict larger ones should be increased to at least a year if the new method is confirmed. EL Nino tends to develop between April and June and reaches its peak between December and February. The warming tends to last between 9 and 12 months and occurs every two to seven years. The new forecasting method does not predict any major EL Nino events in the next two years, although a weak warming toward the end of this year is possible.

The Sahara The name Sahara derives from the Arabic word for “desert“ or “steppe“. At 3.5 million square miles, an area roughly the size of the United States, the Sahara Desert in northern Africa is the largest desert in the world. It spans the continent from the Atlantic Ocean to the Red Sea. Daytime temperatures can reach as high as 130°F. The humidity sometimes gets into the teens. But it can also be as low as 2. 5 percent, the lowest in the world. Most of the Sahara receives less than five inches of rain per year, while large areas sometimes have no rainfall at all for years. At the heart of the Sahara is the landlocked north African country of Niger. Here the sand dunes can be 100 feet tall and several miles long. Here sand plains stretch over an area larger than Germany where there is neither water nor towns. Yet sitting in the midst of the surrounding desert is the town of Bilma. Suddenly there are pools of clear water. Surprisingly, there are groves of date palms. Underground water resources, or oases, sufficient to support irrigated agriculture are found in dry stream beds and depressions. Irrigation ditches run off a creek to water fields. Corn, cassava, tea, peanuts, hot peppers, and orange, lime , and grapefruit trees grow in these fields. Donkeys and goats graze on green grass. The Sahara of Niger is still a region where you can see a camel caravan of 500 camels tied together in loose lines as long as a mile, traveling toward such oasis towns. There a caravan will collect life-sustaining salt, which is mined from watery basins, and transport it up to 400 miles back to settlements on the edges of the desert. The round trip across the vast sands takes one month.

This passage is mostly about______.

Rainfall in most of the Sahara is______.

The Sahara can be described as

The phrase “an area roughly the size of the United States“ gives an indication of the size of

In this passage “caravan“ means