题目

Everyone on the bus saw the pickpocket stealing a purse from a girl. ________, no one dared to stop him. A. Consequently            B. Though      C. Moreover                    D. Nevertheless 答案：D已知圆O1：x2+y2+10x+24=0，圆O2：x2+y2-10x-24=0都内切于动圆，试求动圆圆心的轨迹方程．