题目

It is ___ the customers’ needs that has made chain stores so popular in big cities in China. A. meeting           B. met            C. to have met      D. being met 答案：A如图，在直角坐标系中，点A、B、C的坐标分别为（0，3）（4，3）（0，－1），则△ABC外接圆的圆心坐标为 ．