某同学做“探究求合力的方法”的实验时，主要步骤是：

A．在桌上放一块方木板，在方木板上铺一张白纸，用图钉把白纸钉在方木板上；

B．用图钉把橡皮条的一端固定在板上的A点，在橡皮条的另一端拴上两条细绳，细绳的一端系着绳套；

C．用两个弹簧测力计分别钩住绳套，互成角度地拉橡皮条，使橡皮条伸长，结点到达某一位置O点．记录O点的位置，读出两个弹簧测力计的示数；

D．按选好的标度，用铅笔和刻度尺作出两个弹簧测力计的拉力F₁和F₂的图示，并用平行四边形定则求出合力F；

E．只用一个弹簧测力计，通过细绳套拉橡皮条使其伸长，读出弹簧测力计的示数，记下细绳的方向，按同一标度作出这个力F′的图示；

F．比较F′和F的大小和方向，看它们是否相同，得出结论．

上述步骤中：

有人说，17世纪末的英国国王开始被套上“紧箍咒”。这里的“紧箍咒”是指(    )

B

    A boy and his father walk in the mountains. Suddenly the boy falls, hurts himself, and cries, "AAAhhhhhhhh!!!" To his surprise, he hears the voice(声音) repeating(重复), somewhere in the mountain, "AAAhhhhhhhh!!!" Then the boy cries again, "Who are you?" He hears the answer "Who are you?" He thinks someone else in the mountain is laughing at him, so he gets angry and shouts "Foolish!" He receives the answer "Foolish!"

    He looks at his father and asks, "What's going on?" The father smiles and says, "My son, listen." And then he shouts to the mountain, "I love you!" The voice answers, "I love you!" Again the man cries, "You're the best!" The voice answers, "You're the best!"

    The boy is surprised, but does not understand. Then the father explains(解释), "People call this 'Echo', but really this is life. It gives you back everything you say or do. Our life is just a reflection（反映）of what we have done. If you want more love in the world, have more love in your heart. If you want to be successful(成功), work hard. This can be used in everything in life. Life will give you back everything you have given to it."