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.

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

The discovery of life beyond Earth would transform not only our science but also our religions, our belief systems and our entire world-view. For in a sense, the search for extraterrestrial life is really a search for ourselves--who we are and what our place is in the grand sweep of the cosmos.
Contrary to popular belief, speculation that we are not alone in the universe is as old as philosophy itself. The essential steps in the reasoning were based on the atomic theory of the ancient Greek philosopher Democritus. Yet philosophy is one thing, filling in the physical details is another. Although astronomers increasingly suspect that biofriendly planets may be abundant in the universe, the chemical steps leading to life remain largely mysterious.
Traditionally, biologists believed that life is a freak--the result of a zillion-to-one accidental concatenation of molecules. It follows that the likelihood of its happening again elsewhere in the cosmos is infinitesimal. This viewpoint derives from the second law of thermodynamics, which predicts that the universe is dying--slowly and inexorably degenerating toward a state of total chaos. And similar reasoning applies to evolution. According to the orthodox view, Darwinian selection is utterly blind. Any impression that the transition from microbes to man represents progress is pure chauvinism of our part. The path of evolution is merely a random walk through the realm of possibilities.
If this is right, there can be no directionality, no innate drive forward; in particular, no push toward consciousness and intelligence. Should Earth be struck by an asteroid, destroying all higher life-forms, intelligent beings would almost certainly not arise next time around. There is, however, a contrary view--one that is gaining strength and directly challenges orthodox biology. It is that complexity can emerge spontaneously through a process of self- organization. If matter and energy have an inbuilt tendency to amplify and channel organized complexity, the odds against the formation of life and the subsequent evolution of intelligence could be drastically shortened.
Historically, Bertrand Russell argued that a universe under a death sentence from the second law of thermodynamics rendered human life ultimately futile. All our achievements, all our struggles, "all the noonday brightness of human genius," as he put it, would, in the final analysis, count for nothing if the very cosmos itself is doomed. But what if, in spite of the second law of thermodynamics, there can be systematic progress alongside decay For those who hope for a deeper meaning or purpose beneath physical existence, the presence of extraterrestrial life-forms would provide a spectacular boost, implying that we live in a universe that is in some sense getting better and better rather than worse and worse.

A:opposite. B:similar. C:divergent. D:contrary.

Jane's dress is similar in design ______ her sister's.

A:with B:like C:to D:as

（）is the conscious effort to make all jobs similar, routine, and interchangeable.

A:WWW B:Informatization C:Computerization D:Standardization

The design of _____ is similar to that of the main bearing.

A:the block bearing B:the camshaft bearing C:the connecting rod small end bearing D:the connecting rod large end bearing

The function of a rectifier is similar to that of a _____.

A:trap B:regulating valve C:check valve D:filter

AC and DC generators are similar in that they _____.

A:both generate alternating voltages B:both rectify the voltage before delivery C:are constructed at the same physical size for the same kilowatt rating D:both supply three-phase power

The diesel engine is similar to the gasoline engine in that ______.

A:both of them are ignited by compressed air B:both of them are the forms of external combustion engines C:both of them have spark plugs D:the power is developed by the piston in the cylinder

"________ are used in fog and similar circumstances when visual signals can not be seen．

A:Visual signals B:Substitutes C:Pennant-shaped flags D:The ship's sirenwhistle or bell