一、选择题1.在立体几何中,以下真命题的个数为()①垂直于同一直线的两直线平行②到定点距离等于定长的点的轨迹是圆③有三个角是直角的四边形是矩形④自一点向已知直线引垂线有且只有一条A.0B.1C.2D.32.过四条两两平行的直线中的两条最多可确定的平面个数是()A.3B.4C.5D.63.在 First, multiple-choice questions 1. In the three-dimensional geometry, the following number of true propositions is () 1 The trajectory of two straight lines that are perpendicular to the same straight line 2 to fixed-point distance equal to the fixed-length point is the circle 3 There are three corners that are right-angled quadrilaterals Is the maximum number of planes from which a rectangle 4 can be determined from a point to a known straight line and there is only one A.0B.1C.2D.32. two lines that are parallel by four are parallel to each other () A.3B .4C.5D.63. At