题目

According to the newlymade traffic regulations，whoever drives through the red light ________be fined at least 200 dollars. A．shall                        B．may  C．would                        D．must 答案：A18．在平面直角坐标系xOy中，已知圆C：x2+y2=4和动直线l：x=my+1．（1）证明：不论m为何值时，直线l与圆C都相交；（2）若直线l与圆C相交于A，B，点A关于轴x的对称点为A1，试探究直线A1B与x轴是否交于一个定点？请说明理由．