下列关于栈的描述中，正确的是( )。
A．在栈中只能插入元素而不能删除元素
B．在栈中只能删除元素而不能插入元素
C．栈是特殊的线性表，只能在一端插入或删除元素
D．栈是特殊的线性表，只能在一端插入元素，而在另一端删除元素
参考答案：C
解析： 栈是一种数据结构，它按照先进后出的原则存储数据，先进入的数据被压人栈底，最后进人的数据在栈顶。读数据的时候从栈顶开始弹出数据、栈是只能在一端插入和删除的特殊线性表。
| 完形填空。 | ||||
| It used to be our custom to take handmade baskets to friends on May Day. We would 1 baskets on a doorstep, knock on the door, and then run away as fast as our legs could 2 us. It was delightful to peer (窥视) around a bush and watch our friends open their 3 and pick up the colorful gift, 4 who had left it out for them. I clearly 5 the May Day of the year when I turned ten. That year I was faced with a (an) 6 involving one of my dearest friends, Pam. We had studied and 7 together nearly every day, but things 8 after a new family had moved into our small town. Pam was spending more and more time at their house and I felt 9 and left out. When my mother asked me 10 I was going to take a May Day basket to Pam's house, I responded 11 , "Absolutely not! I hate Pam." I began to cry. Mom wiped away my 12 and told me that things and people change. She explained that one of the greatest things friends can do is to give each other a 13 to grow, to change and to develop, and that it's 14 for one's friends to spend time with other people. I 15 decided to give Pam a basket as a sign of forgiveness, and asked my sister to help me do it. As we watched from our 16 place, Pam picked up the basket and said loudly enough for us to hear, "Thank you, Susie, I hoped you wouldn't 17 me!" That day, I made a 18 that changed my life: I decided to hold my friends tightly in my heart, but 19 in my expectations of them, allowing them 20 to grow and to change-with or without me. | ||||
|