已知函数y₁=ax²+bx，y₂=ax+b（ab≠0）．在同一平面直角坐标系中．

下列物体的三视图与物体摆放位置无关的是（    ）

注意：行文连贯，涵盖要点，适当发挥。词数100左右。
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钢铁在水中是沉的，我们可以改变它的____来让它浮在水面上。