【单选题】
点在直线上，点的正投影一定在该直线的正投影上，点、直线在平面上，点和直线的正投影一定在该平面的正投影上，这种性质称为正投影的（ ）。
①
平行性
②
从属性
③
同素性
④
定比性
【单选题】
根据投射线和轴测投影面相对位置的不同，轴测投影可分（ ）。
①
正轴测投影和斜轴测投影
②
水平轴测投影和竖直轴测投影
③
直轴测投影和歪轴测投影
④
斜二轴测投影和斜三轴测投影
【单选题】
平面的正面投影积聚为一条直线并与OX轴平行，该平面是（ ）。
①
Normal
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②
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正垂面
④
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铅垂面