单选题：The following is the part of depth-first search tree to find the

The following is the part of depth-first search tree to find the articulation points, and the Num(v) value has been marked beside each vertex v. The back edges are not shown. Which of the following situation is impossible? @[C](2)



A. low(v6) is greater than low(v7)
B. low(v4) is 2
C. low(v6) is 3
D. low(v7) is 2






A.low(v6) is greater than low(v7)
B.low(v4) is 2
C.low(v6) is 3
D.low(v7) is 2


答案：C