单选题：Given the popping sequence of a stack as { 1, 2, 3, 4, 5, 6 }. A

Given the popping sequence of a stack as { 1, 2, 3, 4, 5, 6 }. Among the following, the impossible pushing sequence is:
@[D](2)

A. 3 2 1 6 5 4
B. 6 5 1 2 3 4
C. 6 5 4 1 2 3
D. 4 6 5 1 3 2



A.3 2 1 6 5 4
B.6 5 1 2 3 4
C.6 5 4 1 2 3
D.4 6 5 1 3 2


答案：D