[单项选择]

The horse came into existence before man on earth. Although the earliest remains of primitive horses have been found on the North American continent, many scientists believe this small species traveled over a land mass. It became extinct (绝种的) in America. Other scientists believe that the horse may have originated in Asia. In any event the animal soon spread into China, Europe, and the Middle East. The first modem horse to be introduced into the American continent came with the early Spanish explorers. Horses were bred into many types. The heavy horses developed in the low countries of Europe and were used for work and by the medieval knights (中世纪骑士) to fide. The oldest breed of horses is said to be the Arabian. The only true wild horses left in 20th century are found in Mongolia. Horses are said to rate in intelligence after the ape, the elephant, the dog. They have excellent memories and can sometimes find their way home when lost, and sense danger better than their masters. Th
A. For food.
B. For power.
C. To make money.
D. To work for him.

[单项选择]

The horse came into existence before man on earth. Although the earliest remains of primitive horses have been found on the North American continent, many scientists believe this small species traveled over a land mass. It became extinct (绝种的) in America. Other scientists believe that the horse may have originated in Asia. In any event the animal soon spread into China, Europe, and the Middle East. The first modem horse to be introduced into the American continent came with the early Spanish explorers. Horses were bred into many types. The heavy horses developed in the low countries of Europe and were used for work and by the medieval knights (中世纪骑士) to fide. The oldest breed of horses is said to be the Arabian. The only true wild horses left in 20th century are found in Mongolia. Horses are said to rate in intelligence after the ape, the elephant, the dog. They have excellent memories and can sometimes find their way home when lost, and sense danger better than their masters. Th
A. In the Middle East.
B. In Europe.
C. On the North American continent.
D. In Spain.

[单项选择]

Thousands of years before Columbus came to the New World, the American Indians entered North America by crossing a narrow strip of land that once connected Alaska and Siberia. The migrants entered a new world in which there were no people at all. But there were many animals to hunt, and there were forests where nuts, roots and berries could be gathered.
(27) When the Europeans came to the New World, the Indians, at first, taught the settlers how to plant corn, bake fish, make canoes and smoke tobacco. In return, the whites introduced horses, guns, gun-powder and alcohol. But at last, there were struggles for land, and the struggles could have only one result-war. When the wars were over, all Indians were moved to large tracts of land called reservations. Now, some of them, embittered by past mistreatment, are determined to preserve their tribal life; some wish to modernize the reservations. These alternatives, with many variations, are what most Indians have chosen
A. with Columbus
B. before Columbus did
C. after Columbus’ arrival
D. in the 18^th century

[填空题]Before humans came on the scene, the world changed only slowly. The climate warmed and cooled, new plants and animals evolved (进化) and became extinct in their turn, and sea levels rose and fell over periods of thousands, if not millions, of years. But during the last two thousand years there have been very great changes. Forests have disappeared, river courses have been changed, and large areas of natural vegetation have turned into farmland and cities. There are serious problems for the survival of the human race.
The Greenhouse Effect
It may be cold outside, but on a sunny day it can be hot in a greenhouse. Some of the gases in the Earth’s atmosphere act like the glass in a greenhouse. Radiant heat from the Sun can pass through them to warm the Earth below. But the ground also loses heat by radiation (辐射). The "’greenhouse gases" send some of this heat back towards the Earth’s surface and help to keep it warm. However, by burning fuels