如图所示，斜面固定在地面上，倾角为37°(sin37°=0.6，cos37°=0_爱下问搜题

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问题选择题

如图所示，斜面固定在地面上，倾角为37°(sin37°=0.6，cos37°=0.8）。质量为1kg的滑块以初速度v₀从斜面底端沿斜面向上滑行(斜面足够长，该滑块与斜面间的动摩擦因数为0.8)，则该滑块所受摩擦力F_f随时间变化的图象是下图中的（取初速度方向为正方向）(g=10 m/s²)

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A.

B.

C.

D.

答案

答案：B

单项选择题

非处方药物的遴选原则是安全有效、疗效确切、质量稳定和使用方便。下列哪一项属于疗效确切的含义（）

A.处方中无十八反、十九畏

B.不易引起依赖性

C.处方合理，功能主治明确

D.有完善的质量标准，质量可控

E.明确标示药物禁忌

完形填空

Last summer a tornado hit a small town nearby. I saw in the local newspaper a picture of a young woman a little boy and a younger 36 standing in front of a totally destroyed house eyes wide open with 37 .I noticed their clothing 38 closely matched ours. This would be a good opportunity to teach my children to help those less 39.
I   40   their situation to my seven-year-old twins, Brad and Martin, and   41   the boys to donate some of their less favorite toys. My little daughter, Meghan,   42   quietly when the boys piled up the old toys. After a while, Meghan walked up   43   Lucy, her much-loved doll,   44   tightly to her chest. She put her round little   45   into Lucy’s, giving her a final kiss, and then laid her   46   on top of the others. “Oh, honey,” I said，“you don’t have to give Lucy. You love her so much. ”
Meghan nodded, trying to   47   her tears. “Lucy makes me happy, Mummy. Maybe she’ll make that little girl happy, too. ”
The boys watched in surprise   48   their baby sister placed Lucy in the   49  . While I stared at Meghan, reflecting upon my donation, they went, without a word, to their room and both          50   with their valued items. Martin hesitated   51  , then looked over at Meghan and put his model car next to Lucy. Amazed, I removed my old   52   from the box, and   53   it with a new one I had bought the week before, hoping the young woman would   54   it as much.
Anyone can give away what they no longer need, but true generosity is giving what you   55 .     I, who had meant to teach, was taught.

C．demonstrated

D．disappeared