读“我国四个省级行政区轮廓示意图”，完成下列问题。

如图所示，劲度系数k=25N/m轻质弹簧的一端与竖直板P栓接（竖直板P固定在木板B的左端），另一端与质量m_A=1kg的小物体A相连，P和B的总质量为M_B=4kg且B足够长．A静止在木板B上，A右端连与细线绕过光滑的定滑轮与质量m=1kg的物体C相连，木板B的上表面光滑，下表面与地面的动摩擦因数μ=0.4．开始时用手托住C，让细线恰好伸直但没拉力，然后由静止释放C，直到B开始运动．已知弹簧伸长量为x时其弹性势能为 $\frac{1}{2}$ kx²，全过程物体C没有触地，弹簧在弹性限度内，g取10m/s²．求：

先通读下面的短文，掌握其大意，然后从A、B、C三个选项中选择最佳答案。

    Cars are very popular in America. When the kids are fourteen years old. They dream of having their own 1. Many students work after school to 2 a car. In most places 3 people learn to drive in high school. They have to take a 4 test to get a license. Learning to drive and getting a driver's 5 may be one of the most exciting things in their lives. For many, that piece of paper is an important symbol(象征)that they are now grown-ups.

    Americans seem to love their cars almost more than anything else. People almost never go to see a doctor when they are 6. But they will take 7 cars to a “hospital” at the smallest sign of a problem. At weekends, people 8most of the time in washing and waxing(打蜡) their cars. For some families it is not enough to have 9 car. They often have two or even three. Husbands need a car to go to work. Housewives need a car to go shopping or to take the children to school or 10 activities.