题干

如图,质量为M的楔形物块静置在水平地面上,其斜面的倾角为θ.斜面上有一质量为m的小物块,小物块与斜面之间存在摩擦.用恒力F沿斜面向上拉小物块,使之匀速上滑.在小物块运动的过程中,楔形物块始终保持静止.地面对楔形物块的支持力为

A:(M+m)g

B:(M+m)g-F

C:(M+m)g+Fsinθ

D:(M+m)g-Fsinθ

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D

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    One of the easiest things in the world is to become a fault-finder. However, life can be 1when you are not busy finding fault with it.

    Several years ago I2a letter from seventeen-year-old Kerry, who described herself as a world-class fault-finder, almost always 3by things. People were always doing things that annoyed her, and 4was ever good enough. She was highly self-critical and also found fault with her friends. She became a really 5person.

    Unfortunately, it took a horrible accident to change her 6Her best friend was seriously hurt in a car crash. What made it almost 7to deal with was that the day before the 8, Kerry had visited her friend and had spent the whole time criticizing her 9 of boyfriends, the way she was living, the way she related to her mother, and various other things she felt she needed to 10It wasn't until her friend was badly hurt that Kerry became 11her habit of finding fault. Very quickly, she learned to appreciate life rather than to 12 everything so harshly ( 刻薄) . She was able to transfer her new wisdom to other parts of her13as well.

    Perhaps most of us aren't as extreme at fault-finding,14 when we're honest, we can be sharply 15of  the world. I'm not suggesting you16problems, or that you pretend things are17than they are, but simply that you learn to allow things to be as they are—18most of the time, and especially when it's not a really big 19 .

    Train yourself to "bite your tongue" , and with a little 20, you'll get really good at letting things go. And when you do, you'll get back your enthusiasm and love for life.