More people are beginning to buy things through the Internet.Do you think shopping online will take the place of shopping in stores? A.especially B.frequently C.finally D.properly 答案:C点P(x,y,z)满足=2,则点P在( )A.以点(1,1,﹣1)为圆心,以2为半径的圆上B.以点(1,1,﹣1)为中心,以2为棱长的正方体上C.以点(1,1,﹣1)为球心,以2为半径的球面上D.无法确定