In the reaction Zn（s) + 2H+（aq) → Zn2+（aq) + H2（g), Zn（s) is the agent

A scorching sun, an endless sea of sand and a waterless, forbiddingly lonely land--that is the image most people have of deserts. But how true is this picture? Deserts are drylands where rainfall is low. This is not to say rain never falls in deserts. It may fall once or twice a year in a fierce torrent that fades almost as soon as it has begun, or which evaporates in the hot air long before it has got anywhere near the earth. It may fall in a sudden sweeping flood that carries everything in its path. Rains may only come once in five or six years or not fall for a decade or more. The Mojave desert in the United States remained dry for twenty-five years.

Without water no living thing can survive, and one feature of the desert landscape is the absence of vegetation. With little rain and hardly any vegetation the land suffers under the sun. There are virtually no clouds or trees to protect the earth's surface and it can be burning hot. Under the sun, soils break up and crack. Wind and torrential rain sweep away and erode the surface further. Eight million square kilometers of the world's land surface is desert. Throughout history deserts have been expanding and retreating again. Cave paintings show that parts of the Sahara Desert were green and fertile about 10, 000 years ago, and even animals like elephants and giraffes roamed the land. Fossil and dunes found in fertile and damp parts of the world show that these areas were once deserts. But now the creation of new desert areas is happening on a colossal scale. Twenty million square kilometers, an area twice the size of Canada, is at a high to very high risk of becoming desert. With a further 1.25 million square kilometers under moderate risk, an area covering 30% of the earth's land surface is desert, becoming desert, or in danger of becoming desert. The rate of growth of deserts is alarming. The world's drylands which are under threat include some of the most important stock-rearing and wheat-growing areas and are the homes of 600 - 700 million people. These regions are becoming deserts at the rate of more than 58, 000 square kilometers a year or 44 hectares a minute. In North Africa at least 100, 000 hectares of cropland are lost each year. At this rate there is a high risk that we will be confined to living on only 50% of this planet's land surface within one more century unless we are able to do something about it.

What does the passage tell us about rainfall in the desert?

A．It never rains.

B．It rains so little that nothing can live.

C．It rains unexpectedly.

D．It rains very infrequently.

A scorching sun, an endless sea of sand and a waterless, forbiddingly lonely land--that is the image most people have of deserts. But how true is this picture? Deserts are drylands where rainfall is low. This is not to say rain never falls in deserts. It may fall once or twice a year in a fierce torrent that fades almost as soon as it has begun, or which evaporates in the hot air long before it has got anywhere near the earth. It may fall in a sudden sweeping flood that carries everything in its path. Rains may only come once in five or six years or not fall for a decade or more. The Mojave desert in the United States remained dry for twenty-five years.

Without water no living thing can survive, and one feature of the desert landscape is the absence of vegetation. With little rain and hardly any vegetation the land suffers under the sun. There are virtually no clouds or trees to protect the earth's surface and it can be burning hot. Under the sun, soils break up and crack. Wind and torrential rain sweep away and erode the surface further. Eight million square kilometers of the world's land surface is desert. Throughout history deserts have been expanding and retreating again. Cave paintings show that parts of the Sahara Desert were green and fertile about 10, 000 years ago, and even animals like elephants and giraffes roamed the land. Fossil and dunes found in fertile and damp parts of the world show that these areas were once deserts. But now the creation of new desert areas is happening on a colossal scale. Twenty million square kilometers, an area twice the size of Canada, is at a high to very high risk of becoming desert. With a further 1.25 million square kilometers under moderate risk, an area covering 30% of the earth's land surface is desert, becoming desert, or in danger of becoming desert. The rate of growth of deserts is alarming. The world's drylands which are under threat include some of the most important stock-rearing and wheat-growing areas and are the homes of 600 - 700 million people. These regions are becoming deserts at the rate of more than 58, 000 square kilometers a year or 44 hectares a minute. In North Africa at least 100, 000 hectares of cropland are lost each year. At this rate there is a high risk that we will be confined to living on only 50% of this planet's land surface within one more century unless we are able to do something about it.

What does the passage tell us about rainfall in the desert?

A．It never rains.

B．It rains so little that nothing can live.

C．It rains unexpectedly.

D．It rains very infrequently.

A scorching sun, an endless sea of sand and a waterless, forbiddingly lonely land—that is the image most people have of deserts. But how true is this picture? Deserts are drylands where rainfall is low. This is not to say rain never falls in deserts: it may fall once or twice a year in a fierce torrent that fades almost as soon as it has begun, or which evaporates in the hot air long before it has got anywhere near the earth. It may fall in a sudden sweeping flood that carries everything in its path. Rains may only come once in five or six years or not fall for a decade or more. The Mojave desert in the United States remained dry for twenty-five years.

Without water no living thing can survive, and one feature of the true desert landscape is the absence of vegetation. With little rain and hardly any vegetation the land suffers under the sun. There are virtually no clouds or trees to protect the earth's surface and it can be burning hot. Under the sun, soils break up and crack. Wind and torrential rain sweep away and erode the surface further. Eight million square kilometers of the world's land surface is desert. Throughout history deserts have been expanding and retreating again. Cave paintings show that parts of the Sahara Desert were green and fertile about 10,000 years ago, and even animals like elephants and giraffes roamed the land. Fossil and dunes found in fertile and damp parts of the world show that these areas were once deserts. But now the creation of new desert areas is happening on a colossal scale. Twenty million square kilometers, an area twice the size of Canada, is at a high to very high risk of becoming desert. With a further 1.25 million square kilometers under moderate risk, an area covering 30% of the earth's land surface is desert, becoming desert, or in danger of becoming desert. The rate of growth of deserts is alarming. The world's drylands which are under threat include some of the most important stock-rearing and wheat-growing areas and are the homes of 600--700 million people. These regions are becoming deserts at the rate of more than 58, 000 square kilometers a year or 44 hectares a minute. In North Africa at least 100,000 hectares of cropland am lost each year. At this rate there is a high risk that we will be confined to living on only 50% of this planet's land surface within one more century unless we am able to do something about it.

What does the passage tell us about rainfall in the desert?

A．It never rains.

B．It rains so little that nothing can live.

C．It rains unexpectedly.

D．It rains very infrequently.

听力原文： Ozone is a form. of oxygen. It is found in the air we breathe and in the upper atmosphere. Near Earth, ozone ii1 the air is a danger to life because it is a pollutant. (33)But between ten and fifty kilometers up in the atmosphere, ozone protects life on Earth. Ozone forms in the atmosphere through the action of radiation from the sun. Ozone blocks harmful radiation from reaching Earth. Scientists say a decrease in ozone and an increase in the harmful radiation will cause many more cases of skin cancer. And it will harm crops, animals and fish.

(34)Ozone problems first became known in 1985. British scientists reported that ozone levels in the Antarctic atmosphere near the South Pole fell sharply each year in October and November. 1987 was the first year that a huge hole developed in the ozone layer above the Antarctic.

(35)A recent study of the atmosphere over the Arctic area near the North Pole showed extreme thinning of the ozone. Officials from the American space agency said the latest study is a result of the largest campaign yet to measure ozone amounts and changes in the Arctic area. NASA researcher Paul Newman said some of the measurements show ozone in the Arctic decreased about 60% between January and the middle of March. These measurements are similar to the ozone losses observed in this area a few years ago. (35)Other studies have shown that man-made chemicals were destroying ozone in the atmosphere. An international agreement halted production of the most harmful chemicals. (35)The new findings support the idea that recovery of the ozone layer can not be delayed.

(30)

A．In the lower atmosphere.

B．In the upper atmosphere.

C．On the Earth.

D．Near the Earth.

Section B

Directions: In this section, you will hear 3 short passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A, B, C and D.

听力原文： At one time it was the most important city in the region—a bustling commercial center known for its massive monuments, its crowded streets and commercial districts, and its cultural and religious in situations. Then, suddenly, it was abandoned. Within a generation most of its population departed and' the at once magnificent city be came all but a ghost town. This is the history of a pre-Columbia city called Teotihuacán. The name is the Aztec word, which means "the place the god calls home". It was once a metropolis of as many as 2,000,000 inhabitants 33 miles northwest of present-day Mexico City. And it was also the focus of a great empire that stretched from the arid plains of central Mexico to the mountain of Guatemala.

Why did this city die? Researchers have found no signs of epidemic disease or destructive inversions. But they have found signs that suggest the Teotihuacáns themselves burned their temples and some of their other buildings. There were evidence revealed that piles of weed had been placed around these structures and set fire. Some speculate that Teotihuacán's inhabitants may have abandoned the city because it had become "a clumsy giant..." But other experts think that the ancient inhabitants may have destroyed their temples and abandoned their city in rage against their gods for permitting a long famine.

(27)

A．It's near Mexico City.

B．It's in Guatemala.

C．It's stretched from the plains of central Mexico to the mountains of Guatemala.

D．It's in America.

Section B

Directions: In this section, you will hear 3 short passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A, B, C and D.

听力原文： At one time it was the most important city in the region—a bustling commercial center known for its massive monuments, its crowded streets and commercial districts, and its cultural and religious institutions. Then, suddenly, it was abandoned. Within a generation most of its population departed and the at once magnificent city became all but a ghost town. This is the history of a pre-Columbia city called Teotihuacan. The name is the Aztec word, which means "the place the god calls home". It was once a metropolis of as many as 2,000,000 inhabitants 33 miles northwest of present-day Mexico City. And it was also the focus of a great empire that stretched from the arid plains of central Mexico to the mountain of Guatemala.

Why did this city die? Researchers have found no signs of epidemic disease or destructive invasions. But they have found signs that suggest the Teotihuacanos themselves burned their temples and some of their other buildings. There were evidence revealed that piles of wood had been placed around these structures and set fire. Some speculate that Teotihuacan's inhabitants may have abandoned the city because it had become "a clumsy giant..." But other experts think that the ancient inhabitants may have destroyed their temples and abandoned their city in rage against their gods for permitting a long famine.

(27)

A．It's near the Mexico City.

B．It's in Guatemala.

C．It's stretched from the plains of central Mexico to the mountains of Guatemala.

D．It's in America.

Section B

Directions: In this section, you will hear 3 short passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A, B, C and D.

听力原文： At one time it was the most important city in the region--a bustling commercial center known for its massive monuments, its crowded streets and commercial districts, and its cultural and religious institutions. Then, suddenly, it was abandoned. Within a generation most of its population departed and the at once magnificent city became all but a ghost town. This is the history of a pre-Columbia city called Teotihuacan. The name is the Aztec word, which means "the place the god calls home". It was once a metropolis of as many as 2,000,000 inhabitants 33 miles northwest of present-day Mexico City. And it was also the focus of a great empire that stretched from the arid plains of central Mexico to the mountain of Guatemala.

Why did this city die? Researchers have found no signs of epidemic disease or destructive invasions. But they have found signs that suggest the Teotihuacanos themselves burned their temples and some of their other buildings. There were evidence revealed that piles of wood had been placed around these structures and set fire. Some speculate that Teotihuacan's inhabitants may have abandoned the city because it had become "a clumsy giant..." But other experts think that the ancient inhabitants may have destroyed their temples and abandoned their city in rage against their gods for permitting a long famine.

(27)

A．It's near the Mexico City.

B．It's in Guatemala.

C．It's stretched from the plains of central Mexico to the mountains of Guatemala.

D．It's in America.

Part I Reading Comprehension

Directions: There are three passages in this part. 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 and mark the corresponding letter on the Answer Sheet with a single line through the center.

Passage 1

Question 1to 5 are based on the following passage.

Looking back on my childhood. I am convinced that naturalists are born and not made. Although we were brought up in the same way, my brothers and sisters soon abandoned their pressed(紧抱的) flowers and insects. Unlike them ,I hand no ear for music and languages, I was not an early reader and I could not do mental arithmetic.

Before World war I we spent our summer holidays in Hungary. I have only the dim memory of the house we lived in, of my room and my toys. (76) Nor do I recall clearly the large family of grandparents, aunts, uncles and cousins who gathered next door . but I do have a crystal-clear memory of dogs, the farm animals , the local birds and above all ,the insects.

I am a naturalist, not a scientist. I have a strong love of the natural world, and my enthusiasm has led me into varied investigations. I love discussing my favorite topics and enjoy burning the midnight. I love discussing my favorite topics and enjoy burning the midnight oil, reading about other people’s observations and discoveries .then something happens that brings these observations together in my conscious mind. Suddenly you fancy you see the answer to the riddle(谜) ，because it all seems to fit together. This has resulted in my publishing 300 papers and books ,which some might honor with the title of scientific research.

But curiosity ,a keen eye, a good memory and enjoyment of the animal and plant world do not make a scientist; one of the outstanding and essential qualities required is self-discipline, a quality I lack. A scientist can be made .A naturalist is born . If you can combine the two, you get the best of born worlds.

1. According to the author , a born naturalist should first of all be _____

A. full of enthusiasm

B. self-disciplined

C. full of ambition

D. knowledgeable