单项选择题
A.s=<{2,4},{3,5,6},{8}>,t=<{2},{3,6},{8}> B.s=<{2,4},{3,5,6},{8}>,t=<{2},{8}> C.s=<{1,2},{3,4}>,t=<{1},{2}> D.s=<{2,4},{2,4}>,t=<{2},{4}>
A.1,2,3,4 B.1,2,3,5 C.1,2,4,5 D.1,3,4,5
A.无向无环 B.有向无环 C.有向有环 D.无向有环