1.在空间直角坐标系中,点A(7,9,5)关于xOy平面对称的点的坐标为A.(7,9,-5)B.(7,-9,5)C.(-7,9,5)D.(7,-9,-5)2.直线l:√3x一3y+2=0的倾斜角为A.150°B.120°C.60°D.30°3.已知向量a=(x,2,3),b=(3,一4,一3),若(a十b)⊥a,则xA.-4B.4C.一4或1D.4或-1