计算：$\sqrt{12}-{\left(-2011\right)}^0+{\left(\frac{1}{2}\right)}^{-1}+\sqrt{{\left(1-\sqrt{3}\right)}^2}$

亚洲中部雄踞着世界上最高的高原—青藏高原，许多大江大河都从那里发源，奔流入海．如图中，甲、乙两图分别为亚洲大陆沿30°N纬线和80°E经线所作的地形剖面示意图，亚洲的地势特点是（   ）

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阅读下面材料, 从A、B、C、D四个选项中选出最佳选项。

    Jumping rope(绳子)is a sport any student can learn to do．You can jump alone or with a friend．You can also help turn a long rope for many others to jump over．If you jump alone, you will need a short rope which should be just long enough for you．

    A rope should be turned slowly．It must also be turned high enough to let you jump safely．Turning the rope safely needs careful timing．In rope jumping, timing means turning the rope slowly enough so that you can jump over it at the right time without its hitting your feet．

  You will notice that when you jump rope, you breathe(呼吸)faster and your face has a healthy colour．But, if you jump too many times at first, you will get too tired．You must learn when to stop for rest(休息)before you jump again．As you practice, you can increase the number(次数)of times you jump without resting．

点电荷，从静电场中的a点移到b点，其电势能的变化为零，则（   ）