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建立人工湿地公园是解决城市水污染的新思路，根据下图回答相关问题。

除净化水质外，人工湿地还具有旅游观光和蓄洪防旱等多方面的功能，这主要是体现了生物多样性的（）价值。

答案

参考答案：直接价值和间接

多选题

如图在光滑地面上，水平外力F拉动小车和木块一起作无相对滑动的加速运动．小车质量是M，木块质量是m，力大小是F，加速度大小是a，木块和小车之间动摩擦因数是μ，则在这个过程中，木块受到的摩擦力大小是（　　）

A．μma

B．ma

C．

mF
M+m

D．F-Ma
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单项选择题

The number of people 85 or older in the United States started increasing dramatically during the last ten years. The good health care that these people enjoyed in the United States during their vulnerable childhood years is primarily responsible for this trend.
Which of the following, if true, most seriously weakens the explanation above

A．Seventy-five percent of the people in the United States who are 85 or older are the children of people who themselves lived leas than 65 years.

B．The people in the United States who are now 85 represent an age group that was smaller in numbers at birth than the immediately preceding and succeeding age groups.

C．Thirty-five percent of the people in the United States who are 85 or older require some form of twenty-fourhour nursing care.

D．Many of the people in the United States who are 85 or older immigrated to the United States when they were 20 years old or older.

E．(E) Because of decreased federal funding for medical care for pregnant mothers and for children, the life expectancy of United States citizens is likely to decrease.
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