问题 问答题 论述题

某地红砂岩,已按规定将其磨细,过筛。烘干后称取50g,用李氏瓶测得其体积为18.9cm3。另有卵石经过清洗烘干后称取1000g,将其浸水饱和后用布擦干。又用广口瓶盛满水,连盖称得其质量为790g,然后将卵石装入,再连盖称得其质量为1409g,水温为25℃,求红砂岩及卵石的密度或视密度,并注明哪个是密度或视密度。

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D

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.

We can conclude from the text that().

A. American cities are changing far the worse

B. people have different views on American cities

C. many people are now moving from American cities

D. the population is decreasing in older American cities