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问题 不定项选择

一质量为10kg的物体位于光滑的水平面上，在水平力F作用下物体沿x轴做直线运动，力F随坐标x的变化如图，物体在x=0处，速度大小为1m/s，则物体运动到x=16m处时速度的大小为

[ ]

A.  

B.2 m/s

C.3 m/s  

D.

答案

答案：C

单项选择题

In a recent year California produced an orange crop equal to only seventy-six percent of Florida’s orange crop. However, when citrus crops as a group, including oranges, were compared, the California crop was twenty-three percent greater than Florida’s crop for the same year.
If the information above is true, which of the following can properly be concluded about the Florida and California citrus crops in the year mentioned

A．Florida’s climate was suited only to growing oranges.

B．Florida produced larger oranges than California did.

C．California produced more oranges than it did non-orange citrus.

D．California’s proportion of non-orange citrus crops was higher than Florida’s.

E．(E) California had more acreage that could be devoted to agriculture than did Florida.
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单项选择题

青年男性，腰痛，腰僵硬，渐出现驼背，X线见骶髂关节模糊，间隙消失。

最支持诊断的检查

A．ESR升高

B．类风湿因子阴性

C．HLA-B27阳性

D．白细胞升高

E．血小板减少
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