The world's thickest book is 12.5 inches.

An international team of scientists is studying the problem

of pollution and dust in Asia. One hundred thirty scientists

from twelve countries have gathered in the western Pacific

area to observe thick dust storms. They will observe the

dust storms which they mix with some of the world's heaviest 【M1】 ______

pollution. The thickest dust storms in recent years

reported in Beijing, China and other Asian cities last spring. 【M2】 ______

The dust storms come from deserts in China and Mongolia. 【M3】 ______

This year, similar dust storms have began moving east 【M4】 ______

toward large Asian cities and the northwest Pacific Ocean.

The dust storms happen in winter over deserts high 【M5】 ______

below sea level. In the spring, the storms trove east, over large

dries in China, Japan and Korea. By summer, rainstorms break

up the dust and help increase pollution in the air. 【M6】 ______

The scientists plan observe the dust storms through the 【M7】 ______

middle of May. They are using research ships, airplanes, satellites

and instrument on the ground to gather information. 【M8】 ______

Aerosols(悬浮颗粒) are very small particles in the air.

The scientists are studying aerosols that contain sulfate(硫酸

盐) and carbon are produced by the burning of soft coal, wood 【M9】 ______

and plants. Barry Hubert of the University of Hawaii is the leading

investigators for the study. He says developing nations in Asia 【M10】 ______

use a mixture of fuels that are not used in other areas.

【M1】

as a ready-made model with which to compare them. The computer model is not perfect, however. For a start, the largest mainframe. (主计算机)in the world can not compete with the potential brain power of human beings. Packed into even the thickest of human skulls are some 1,000 billion cells, or neurons, and each one can connect with thousands of its neighbors. Each connection represents a 'bit' of information and, in theory, we can carry more bits than there are atoms in the known universe.

There are two quite distinct types of memory-short-term and long-term. Our short-term memories are those which we hold on to for just as long as we need them. The vast majority of our everyday thoughts, sights and impressions are registered in the short-term memory only. They take the form. of patterns, or linked pathways, created by circulating currents of electrical energy. So long as the current is buzzing around its little route, the memory that it represents stays in the mind. But once the current dies down, the memory, too, starts to fade. While short-term memories consist of active electrical circuits, long-term memories are quite literally etched (铭刻) into our brains. It seems that if the pathways taken by a particular electrical current are well-trodden, or if the current passing along them is strong enough, the cells along the way change, so that the route or pattern is permanently marked.

Events which have strong meaning for us are particularly likely to be upgraded into the long-term memory. Part of the reason is probably that we go over and over these memories, keeping the pathways stimulated and the electrical current high. It's also likely that certain chemicals come into play, too. When we are excited, very happy, or frightened, our glands pump out chemicals such as adrenaline. One theory has it that some of these chemicals stimulate the neurons to alter their structure and forge permanent connections with each other.

It follows, then, that a memory formed when we are 'up' is more likely to stick than one registered when we are down. Several experiments seem to bear this out. In one, a group of students was first shown an exciting film, then given a list of words to memorize. Another group was shown a miserable film, then given the same learning task. Next day the group who watched the happy film could remember 20% more words than the other group.

About the memory in comparison with the computer the writer says that ______.

A．neither of them is completely reliable all the time

B．the memory is more complicated than the computer

C．the computer operates in a more organized way than the memory

D．neither of them is used to its fullest capacity all the time

A、have ever read

B、had ever read

C、have been reading

D、had ever been reading

o perhaps more than 16 million degrees at the center. The Sun is so much hotter than the Earth that matter can exist only as a gas, except at the core. In the core of the Sun, the pressures are so great against the gases that, despite the high temperature, there may be a small solid core. However, no one really knows, since the center of the Sun can never be directly observed. Solar astronomers do know that the Sun is divided into five layers or zones. Starting at the outside and going down into the Sun, the zones are the corona, chromosphere, photosphere, convection zones, and finally the core. The first three zones are regarded as the Sun' s atmosphere. But since the Sun has no solid surface, it is hard to tell where the atmosphere ends and the main body of the Sun begins. The Sun's outermost layer begins about 10,000 miles above the visible surface and goes outward for millions of miles. This is the only part of the Sun that can be seen during an eclipse such as the one in February 1979. At any other time, the corona can be seen only when special instruments are used on cameras and telescopes to shut out the glare of the Sun's rays. The corona in brilliant, pearly white, filmy light, about as bright as the full Moon. Its beautiful rays are a sensational sight during an eclipse. The corona' s rays flash out in a brilliant fan that has wispy spike-like rays near the Sun's north and south poles. The corona is thickest at the Sun's equator. The corona rays are made up of gases streaming outward at tremendous speeds and reaching a temperature of more than 2 million degree Fahrenheit. The rays of gas thin out as they reach the space around the planets. By the time the Sun's corona rays reach the Earth, they are weak and invisible.

The temperature at the center of the Sun is much higher than it is at the surface.

A．Right

B．Wrong

C．Not mentioned

ses to perhaps more than sixteen million degrees at the center. The sun is so much hotter than the earth that matter can exist only as a gas, except at the core. In the core of the sun, the pressures are so great against the gases that, despite the high temperature, there may be a small solid core. However, no one really knows, because the center of the sun can never be directly observed.

Solar astronomers do know that the sun is divided into five layers or zones. Starting at the outside and going down into the sun, the zones are the corona, chromosphere , photosphere, convection and the sun has no solid surface, so it is difficult to tell where the atmosphere ends and the main body of the sun starts.

The sun's outermost layer begins about 10,000 miles above the visible surface and goes out ward for millions of miles. This is the only part of the sun that can be seen during an eclipse such as the one in February 1979. At any other time, the corona can be seen only when special instruments are used on cameras and telescopes to shot out glare of the sun's rays.

The corona is a bright, pearly white, filmy light, about as bright as the full moon. Its beautiful

rays are a sensational sight during an eclipse. The corona's rays flash out in a brilliant fan that has wispy (纤细的) spikelike rays near the sun's north and south poles. The corona is thickest at the sun's equator.

The corona rays are made up of gases streaming outward at tremendous speeds and reaching a temperature of more than two million degrees Fahrenheit. The rays of gas thin out as they reach the space around the planets. By the time the sun's corona rays reach the earth, they are weak and invisible.

The second paragraph is mainly concerned with ____________.

A．how the sun evolved

B．the structure of the sun

C．why scientists study the sun

D．the distance of the sun from the planets

Section B

Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.

The temperature of the Sun is over 5,000 degrees Fahrenheit at the surface, but it rises to perhaps more than 16 million degrees at the center. The Sun is so much hotter than the Earth that matter can exist only as a gas, except all the core. In the core of the Sun, the pressures are so great against the gases that, despite the high temperature, there may be a small solid core. However, no one really knows, since the center of the Sun can never be directly observed.

Solar astronomers do know that the Sun is divided into five layers or zones. Starting at the outside and going down into the Sun, the zones are the corona (光环圈), chromospheres (色环层), photosphere, convection zone, and finally the core. The first three zones are regarded as the Sun's atmosphere. But since the Sun has no solid surface, it is hard to tell where the atmosphere ends and the main body of the Sun begins.

The sun's outermost layer begins about 10,000 miles above the visible surface and goes outward for millions of miles. This is the only part of the Sun that can be seen during an eclipse. such as the one in February 1979. At any other time, the corona can be seen only when special instruments are used on cameras and telescopes to shut out the glare of the Sun's rays.

The corona is a brilliant, pearly white, filmy light, about as bright as the full Moon. Its beautiful rays are a sensational sight during an eclipse. The corona's rays flash out in a brilliant fan that has wispy (稀疏的) spikelike (穗状的) rays near the Sun's north and south poles. The corona is the thickest at the sun's equator.

The corona rays are made up of gases streaming outward at tremendous speeds and reaching a temperature of more than 2 million degrees Fahrenheit. The rays of gas thin out as they reach the space around the planets. By the time the Sun's corona rays reach the Earth, they are weak and invisible.

With what topic is the second paragraph mainly concerned？

A．How the Sun evolved.

B．The structure of the Sun.

C．Why scientists study the Sun.

D．The distance of the Sun from the planets.

TEXT C

The temperature of the Sun is over 5,000 degrees Fahrenheit at the surface, but it rises to perhaps more than 16 million degrees Fahrenheit at the center. The Sun is so much hotter than the Earth that matter can exist only as a gas, except at the core. In the core of the Sun, the pressures are so great against the gases that, despite the high temperature, there may be a solid core. However, no one really knows, since the center of the Sun can never be directly observed.

Solar astronomers do know that the Sun is divided into five layers or zones. Starting at the outside and going down into the Sun, the zones are the corona, chromosphere, photosphere, convection zone, and finally the core. The first three zones are regarded as the Sun's atmosphere. But since the Sun has no solid surface, it is hard to tell where the atmosphere ends and the main body of the Sun begins.

The Sun's outermost layer begins about 10,000 miles above the visible surface and goes outward for millions of miles. This is the only part of the Sun that can be seen during an eclipse such as the one in February 1979. At any other time, the corona can be seen only when special instruments are used on cameras and telescopes to shut out the glare of the Sun's rays.

The corona is a brilliant pearly white, filmy light, as bright as the full Moon. Its beautiful rays are a sensational sight during an eclipse. The corona's rays flash out in a brilliant fan that has wispy spike-like rays near the Sun's north and south poles. The corona is thickest at the Sun's equator.

The corona rays are made up of gases streaming outward at tremendous speeds and reaching a temperature of more than 2 million degrees Fahrenheit. The rays of gas thin out as they reach the space around the planets. By the time the Sun's corona rays reach the Earth, they are weak and invisible.

Matter on the Sun except at the core can exist only in the form. of gas because of the Sun's

[A] size.

[B] age.

[C] location.

[D] temperature.