The average life expectancy of the Red Indians is ________.
A. higher than the national average
B. lower than the national average
C. about the same with the national average
D. none of the above
A trend that occurs at the same time with the movement to the South and the Weast of the United States is ________.
A. the flow of people to sunbelt area
B. the flow of peole from small cities to big cities
C. the growth of small towns
D. the outflow of city residents from the core cities to the suburbs
液态水具有流动性和粘滞性，两者具有相互关系，液体运动时的粘滞阻力能够使液体的流动加快起来（）
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