What can be inferred from paragraph 3 about annual crops and common property lands？
A. They have been part of agriculture for only the past fifty years．
B. They are not considered to be significant causes of soil degradation．
C. They produce more income than perennial crops and private lands do．
D. They may decrease soil fertility and agricultural productivity．
查看答案
The word patches in paragraph 5 is closest in meaning to
A. dark places
B. family groups
C. warm spots
D. small areas
According to the passage, at what point did writing begin to have a major effect on communication？
A. When alphabets were developed
B. When books became available
C. When education was formalized
D. When the telegraph was invented
Which of the following is an indirect indicator of a population's density？
A. The distribution of food in a given area
B. The number of nests in a given area
C. The number of births in a given period of time
D. The number of individuals counted in a given area
The word thwarted in paragraph 4 is closest in meaning to
A. preceded
B. ended
C. concealed
D. inspired
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