题目

点(3,9)关于直线x+3y-10=0对称的点的坐标是(    )A.(-1,-3)            B.(17,-9)             C.(-1,3)             D.(-17,9) 答案：提示：设所求点的坐标为（x0,y0）,则解得答案：AShe insisted that we ________ the source of the river and begin our journey there. A．find B．found C．had found D．would find