American cities are similar to other cities around the world: In every country, cities reflect the values of the culture. American cities are changing, just as American society is changing.
After World War U , the population of most large American cities decreased ; however, the population in many Sun Belt cities increased. Los Angeles and Houston are cities where population shifts(转移) to and from the city reflect the changing values of American society. In the late 1940s and early 1950s, city residents (居民) became wealthier. They had more children so they needed more space. They moved out of their apartments in the city to buy their own homes. They bought houses in the suburbs (郊区).
Now things are changing. The children of the people who left the cities in the 1950s are now adults. Many, unlike their parents, want to live in the cities. They continue to move to Sun Belt cities and older ones of the Northeast and Midwest. Many young professionals are moving back into cities. They prefer the cities to the suburbs because their jobs are there; or they just enjoy the excitement and possibilities that the city offers.
This population shift is bringing problems as well as benefits. Countless poor people must leave their apartments in the city because the owners want to sell the buildings or make apartments for sale instead of renting, In the 1950s, many poor people did not have enough money to move to the suburbs; now many of these same people do not have enough money to stay in the cities.
Only a few years ago, people though that the older American cities were dying. Some city residents now see a bright, new future. Others see only problems and conflicts. One thing is sure: many dying cities are alive again.

What does the author think of cities all over the world（　）.

A:They are alive. B:They are hopeless. C:They are similar. D:They are different.

Prolonging Human Life
Prolonging human life has increased the size of the human population. Many people alive today would have died of childhood diseases if they had been born 100 years ago. Because more people live longer, there are more people around at any given time. In fact, it is a decrease in death rates, not an increase in birthrates, that has led to the population explosion.
Prolonging human life has also increased the dependency load. In all societies, people who are disabled or too young or too old to work are dependent on the rest of society to provide for them. In hunting and gathering cultures, old people who could not keep up might be left behind to die. In times of famine, infants might be allowed to die because they could not survive if their parents starved, whereas if the parents survived they could have another child. In most contemporary societies, people feel a moral obligation to keep people alive whether they can work or not. We have a great many people today who live past the age at which they want to work or are able to work; we also have roles which require people to retire at a certain age. Unless these people were able to save money for their retirement, somebody else must support them. In the United States many retired people live on social security checks which are so little that they must live in near poverty. Older people have more illness than young or middle-aged people; unless they have wealth or private or government insurance, they must often "go on welfare” if they have a serious illness.
When older people become senile or too weak and ill to care for themselves, they create grave problems for their families. In the past and in some traditional cultures, they would be cared for at home until they died. Today, with must members of a household working or in school, there is often no one at home who can care for a sick or weak person. To meet this need, a great many nursing homes and convalescent hospitals have been built. These are often profit-making organizations, although some are sponsored by religious and other nonprofit groups. While a few of these institutions are good, most of them are simply "dumping grounds" for the dying in which "care" is given by poorly paid, overworked, and underskilled personnel.

It can be inferred from the passage that in hunting and gathering cultures（　）

A:it was a moral responsibility to keep old-aged people alive. B:infants could be left dead in times of starvation. C:parents had to impart the cultural wisdom of the tribe to their children. D:death was considered to be freedom from hardships.

The whale is a mammal-warm-blooded, air-breathing, giving birth to its young alive. sucking them-and, like all mammals, originated on land. There are many signs of this. Its front flippers (鳍足), used for steering and stability, are traces of feet.
Immense strength is built into the great body of the big whales, and in fact most of a whale’s body is one gigantic muscle. The blue whale’s pulling strength has been estimated at 400 horsepower. One specimen was reported to have towed (牵引) a whaling vessel for seven hours at the rate of eight knots.
An enraged whale will attack a ship. A famous example of this was the fate of whaler Essex, which was sunk off the coast South America early in the last century. More recently, steel ships have had their plates buckled in the same way. Sperm whales were known to seize the old-time whaleboats in their jaws and crush them.
The greatest mystery of whales is their diving ability. The sperm whale can dive on the bottom for his favorite food, the octopus. In that search he is known to go as far down as 3,200 feet, where the pressure is 1,400 pounds, to the square inch. Doing so he will remain submerged as long as one hour. Two feats(壮举) are involved in this: storing up enough oxygen (all whales are air-breathed) and withstanding the great change in pressure. Just how he does it scientists have not determined. It is believed that some of the oxygen is stored in a special system of blood vessels, rather than just held in the lungs. And it is believed that a special kind of oil in his head is some sort of compensating mechanism that automatically adjusts the internal pressure of his body. But since you can’t bring a live whale into the laboratory for study, no one knows just how these things work.
Which of the following is a sign of the fact that the whale originated from the land

A:Warm-bloodedness. B:Air-breathing. C:Giving birth to its young alive. D:Its front flippers.

阅读下面的短文，文中有15处空白，每处空白给出4个选项，请根据短文的内容从4个选项中选择1个最佳答案。

A:alive B:awake C:active D:alone

Prolonging human life has increased the size of the human population. Many people alive today would have died of childhood diseases if they had been born 100 years ago. Because more people live longer, there are more people around at any given time. In fact, it is a decrease in death rates, not an increase in birthrates, that has led to the population explosion.
Prolonging human life has also increased the dependency load. In all societies, people who are disabled or too young or too old to work are dependent on the rest of society to provide for them. In hunting and gathering cultures, old people who could not keep up might be left behind to die. In times of famine, infants might be allowed to die because they could not survive if their parents starved, whereas if the parents survived they could have another child. In most contemporary societies, people feel a moral obligation to keep people alive whether they can work or not. We have a great many people today who live past the age at which they want to work or are able to work; we also have rules which require people to retire at a certain age. Unless these people were able to save money for their retirement, somebody else must support them. In the United States many retired people live on social security checks which are so little that they must live in near poverty. Older people have more illnesses than young or middle-aged people; unless they have wealth or private or government insurance, they must often "go on welfare" if they have a serious illness.
When older people become senile or too weak and ill to care for themselves, they create grave problems for their families. In the past and in some traditional cultures, they would be cared for at home until they died. Today, with most members of a household working or in school, there is often no one at home who can care for a sick or weak person. To meet this need, a great many nursing homes and convalescent hospitals have been built. These are often profit-making organizations, although some are sponsored by religious and other nonprofit groups. While a few of these institutions are good, most of them are simply "dumping grounds" for the dying in which "care" is given by poorly paid, overworked, and underskilled personnel.
It can be inferred from the passage that in hunting and gathering cultures ______.

A:it was a moral responsibility to keep old-aged people alive B:infants could be left dead in times of starvation C:parents had to impart the cultural wisdom of the tribe to their children D:death was considered to be freedom from hardships

? ?Prolonging human life has increased the size of the human population. Many people alive today would have died of childhood diseases if they had been born 100 years ago. Because more people live longer, there are more people around at any given time. In fact, it is a decrease in death rates, not an increase in birthrates, that has led to the population explosion.
? ?Prolonging human life has also increased the dependency load. In all societies, people who are disabled or too young or too old to work are dependent on the rest of society to provide for them. In hunting and gathering cultures, old people who could not keep up might be left behind to die. In times of famine, infants might be allowed to die because they could not survive if their parents starved, whereas if the parents survived they could have another child. In most contemporary societies, people feel a moral obligation to keep people alive whether they can work or not. We have a great many people today who live past the age at which they want to work or are able to work; we also have rules which require people to retire at a certain age. Unless these people were able to save money for their retirement, somebody else must support them. In the United States many retired people live on social security checks which are so little that they must live in near poverty. Older people have more illnesses than young or middle-aged people; unless they have wealth or private or government insurance, they must often "go on welfare" if they have a serious illness.
? ?When older people become senile or too weak and ill to care for themselves, they create grave problems for their families. In the past and in some traditional cultures, they would be cared for at home until they died. Today, with most members of a household working or in school, there is often no one at home who can care for a sick or weak person. To meet this need, a great many nursing homes and convalescent hospitals have been built. These are often profit-making organizations, although some are sponsored by religious and other nonprofit groups. While a few of these institutions are good, most of them are simply "dumping grounds" for the dying in which "care" is given by poorly paid, overworked, and underskilled personnel.

It can be inferred from the passage that in hunting and gathering cultures______.

A:infants could be left dead in times of starvation B:it was a moral responsibility to keep old-aged people alive C:death was considered to be freedom from hardships D:parents had to impart the cultural wisdom of the tribe to their children

American cities are similar to other cities around the world: In every country, cities reflect the values of the culture. American cities are changing, just as American society is changing.
After World War U , the population of most large American cities decreased ; however, the population in many Sun Belt cities increased. Los Angeles and Houston are cities where population shifts(转移) to and from the city reflect the changing values of American society. In the late 1940s and early 1950s, city residents (居民) became wealthier. They had more children so they needed more space. They moved out of their apartments in the city to buy their own homes. They bought houses in the suburbs (郊区).
Now things are changing. The children of the people who left the cities in the 1950s are now adults. Many, unlike their parents, want to live in the cities. They continue to move to Sun Belt cities and older ones of the Northeast and Midwest. Many young professionals are moving back into cities. They prefer the cities to the suburbs because their jobs are there; or they just enjoy the excitement and possibilities that the city offers.
This population shift is bringing problems as well as benefits. Countless poor people must leave their apartments in the city because the owners want to sell the buildings or make apartments for sale instead of renting, In the 1950s, many poor people did not have enough money to move to the suburbs; now many of these same people do not have enough money to stay in the cities.
Only a few years ago, people though that the older American cities were dying. Some city residents now see a bright, new future. Others see only problems and conflicts. One thing is sure: many dying cities are alive again.

What does the author think of cities all over the world（　）.

A:They are alive. B:They are hopeless. C:They are similar. D:They are different.

American cities are similar to other cities around the world: In every country, cities reflect the values of the culture. American cities are changing, just as American society is changing.
After World War U , the population of most large American cities decreased ; however, the population in many Sun Belt cities increased. Los Angeles and Houston are cities where population shifts(转移) to and from the city reflect the changing values of American society. In the late 1940s and early 1950s, city residents (居民) became wealthier. They had more children so they needed more space. They moved out of their apartments in the city to buy their own homes. They bought houses in the suburbs (郊区).
Now things are changing. The children of the people who left the cities in the 1950s are now adults. Many, unlike their parents, want to live in the cities. They continue to move to Sun Belt cities and older ones of the Northeast and Midwest. Many young professionals are moving back into cities. They prefer the cities to the suburbs because their jobs are there; or they just enjoy the excitement and possibilities that the city offers.
This population shift is bringing problems as well as benefits. Countless poor people must leave their apartments in the city because the owners want to sell the buildings or make apartments for sale instead of renting, In the 1950s, many poor people did not have enough money to move to the suburbs; now many of these same people do not have enough money to stay in the cities.
Only a few years ago, people though that the older American cities were dying. Some city residents now see a bright, new future. Others see only problems and conflicts. One thing is sure: many dying cities are alive again.

What does the author think of cities all over the world（　）.

A:They are alive. B:They are hopeless. C:They are similar. D:They are different.