题目

They considered __________ a computer, which was considered __________ a great help in their work. A. to buy; to be    B. buying; being       C. to buy; being   D. buying; to be 答案：D图中10个点相邻两个点的距离都等于1，则图中的任意4个点为顶点的所有四边形中有多少个矩形？有多少个相邻的边长分别为1和2的平行四边形？有多少个腰长为1的等腰梯形？