单选题

输入序列为ABCD，可以变为ADCB时，经过的栈操作为（）

Question

A. push, pop, push, pop, push, push, pop, pop

B. push, push, push, push, pop, pop, pop, pop

C. push, push, pop, pop, push, pop, push, pop

D. push, pop, push, push, push, pop, pop, pop