1     By the end of the 1920s, American society had undergone a long and historic demographic change. Since the 1870s, the country had been moving from a more rural mode that was based on high birthrates- as high as 50 births annually per thousand people in the early nineteenth century-to a more metropolitan mode. Prior to the 1870s, the population of the country was increasing by about a third every decade; however, by the end of the 1920s, a radical about-face had taken place.

2     One major factor to affect the demographics of the country during this period was a dramatic decrease in birthrates. The trend during this era was more pronounced in urban areas but also had an effect in rural areas. As a result of the trend toward smaller families, particularly in cities, the birthrate was down to 27.7 births annually per thousand women by 1920 and had dropped even further-to 21.3 births annually per thousand women-by 1930.

3     At the same time, the deathrate, too, was falling. Urban living led to better sanitation, refrigeration, and water purification; it also resulted in better medical care as doctors and hospitals were more readily available. Most likely as a result of these factors, there were only eleven deaths per thousand annually by the early 1920s, which was half the rate of the 1880s.

5. Why does the author include the phrase as high as 50 births annually per thousand people in the early nineteenth century in paragraph 1?

  (A) To show that metropolitan areas of the country had higher birthrates than rural areas

  (B) To provide statistical evidence of the elevated birthrate in the 1870s

  (C) To quantify what had happened with the American population in the previous century

  (D) To argue against the belief that the demographics of the country had changed

6. The author uses the word however in paragraph 1 in order to

  (A) to make it clear that an extreme change had taken place

  (B) to emphasize how tremendously the population was increasing

  (C) to point out an alternate explanation for the change

  (D) to indicate a difference of opinion with other demographers

7. The author includes the word too in paragraph 3

  (A) to indicate that both the birthrate and the deathrate were holding steady

  (B) to show that the rural mode was similar to the metropolitan mode

  (C) to clarify the explanation that population trends before and after 1870 were similar

  (D) to emphasize that paragraph 3 discusses a second factor in the demographic change

8. Why does the author mention better medical care in paragraph 3?

  (A) It helps to explain why the birthrate is increasing.

  (B) It is an example of a factor that contributed to the improved birthrate.

  (C) It helps to explain why the deathrate is increasing.

  (D) It is an example of a factor that contributed to the improved deathrate.

9. The author includes the expression Most likely in paragraph 3 to show

  (A) that the data about the average number of deaths was not verified

  (B) that doctors and hospitals may not have actually been more available

  (C) that other factors may have contributed to the decreasing deathrate

  (D) that the deathrate may not have decreased as much as stated

正确答案： B_A_D_D_C