听力原文: The farm economy of the United States has changed a lot in tile last seventy years. In the 1930s, 25 percent of the nation's population lived on farms (32) . Today less than one percent of Americans do.
Farm incomes have changed over the years too. For example, in 1933, people living and working on farms had much less money to spend than other Americans. At that time, farm families had about one-third the income of non-farmers after all necessary expenses had been paid. By the late 1970s, however, that difference had almost disappeared (33) .
In 2004, farmers had their best year ever. The United States Department of Agriculture says the average farm family earned about 81,000 dollars. That is more than the average American family, which earned about 60,000 dollars. Yet these numbers do not completely explain the situation for all farmer.. Those who have small farms often take other jobs to earn extra income. And farm earnings for large farms grew faster than for small ones (34) .
The Department of Labor measures the pay of industrial workers differently. It measures the average hourly and weekly pay for industrial workers. This is because factory workers are generally paid by the hour unlike farmers who earn income from their farm businesses. Industrial workers are about 23 percent of the labor force. But that number has been decreasing (35) . Most Americans have jobs that provide services. Professional technical and other services employ about 76 percent of the labor force.
(33)
A.About 25 percent of the population.
B.Less than 23 percent of the population.
C.About 76 percent of the population.
D.Less than 1 percent of the population.
第1题
设有如下关系模式:R(A,B,C,p,E),其中R上函数依赖集为:F={(A,B)→E,E→C, C→D}。在函数依赖的范围内该关系模式最高属于()。
A.1NF
B.2NF
C.3NF
D.BCNF
第2题
设有关系模式R(A,B,C),根据语义有如下函数依赖集:F={A→B,(B,C)→A}关系模式R的规范化程度最高达到()。
A)1NF
B)2NF
C)3NF
D)BCNF
第3题
设有如下关系模式:R(A,B,C,D,E),其中R上函数依赖集为:F={(A,B)→E,E→C,C→D}。则在函数依赖的范围内该关系模式最高属于()。
A.1NF
B.2NF
C.3NF
D.BCNF
第4题
设有关系模式R(A,B,C) ,根据语义有如下函数依赖集:F={A→B,(B,C) →A}。关系模式R的规范化程序最高达到
A.1NF
B.2NF
C.3NF
D.BCNF
第5题
设有关系模式R(A,B,C),根据语义有如下函数依赖集:F={A→B,(B,C)→ A}。关系模式R的规范化程度最高达到()。
A.1NF
B.2NF
C.3NF
D.BCNF
第6题
设有关系R(A,B,C),其函数依赖集F={A→B,B→C},则关系R在函数依赖的范畴内最多满足
A.1NF
B.2NF
C.3NF
D.BCNF
第7题
设有关系模式R(A,B,C) ,根据语义有如下函数依赖集:F={A→B,(B,C) →A}。关系模式R的规范化程度最高达到
A.1NF
B.2NF
C.3NF
D.4NF
第8题
设有关系模式R(A,B,C),根据语义有如下函数依赖集:F={A→B,(B,C)→A}。关系模式R的规范化程度最高达到()。
A.1NF
B.2NF
C.3NF
D.BCNF
第9题
设有关系模式R(A,B,C),根据语义有如下函数依赖集:F={A→B,(B,C)→A}。关系模式R的规范化程度最高达到______。
A.1NF
B.2NF
C.3NF
D.BCNF
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