2/5,3/7,4/10,6/14,8/20,12/28,()A.224/56B.14/32C.20/48D.16/40 2/5, 3/7, 4/10, 6/14, 8/20, 12/28, ()A.224/56B.14/32C.20/48D.16/40 参考答案 查看答案