已知一个图的顶点集V={1,2,3,4,5,6,7};边集E={(1,2)3, (1,3)5, (1,4)8, (2,5)10, (2,3)6, (3,4)15, (3,5)12, (3,6)9, (4,6)4, (4,7)20, (5,6)18, (6,7)25},用克鲁斯卡尔算法得到最小生成树,则在最小生成树中依次得到的各条边为()。
A. (1,2)3, (4,6)4, (1,3)5, (1,4)8, (2,5)10, (4,7)20
B. (1,2)3, (4,6)4, (1,3)5, (2,3)6, (1,4)8, (3,6)9
C. (1,2)3, (1,3)5, (1,4)8, (4,6)4, (2,5)10, (4,7)20
D. (1,2)3, (1,3)5, (1,4)8, (2,5)10, (4,6)4, (4,7)20