如果进栈序列为e1、e2、e3、e4，则可能的出栈序列是（）。 A．e

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问题单项选择题

如果进栈序列为e1、e2、e3、e4，则可能的出栈序列是（）。

A．e3、e1、e4、e2

B．e2、e4、e3、e1

C．e3、e4、e1、e2

D．任意顺序

答案

参考答案：B

解析：

由栈“后进先出”的特点可知：A选项中e1不可能比e2先出，C选项中e3不可能比e4先出，且e1不可能比e2先出；D选项中栈是先进后出的，所以不可能是任意顺序：B选项中出栈过程如下图所示。

选择题

观察下图，下列相关的叙述正确的是

改错题

短文改错

This afternoon I went to see my grandfather by a bus. It was very

crowded and I had to stand. Besides me there was a woman held a little boy

in her arms. In front of her, a young man occupies two seats, pretending to be

sleeping. I heard the little boy curious asking his mother, “What’s wrong with

the uncle?” I had thought if perhaps the woman would blame the man.

Beyond her expectations, the woman answered with a smile, “Be quiet. This

uncle must very tired because of hard work.” The young man must have

heard the word. His face turned red and offered one seat for the woman at once.