问题 单项选择题

下面关于B和B+树的叙述中,不正确的是

A.B树和B+树都是平衡的多分树

B.B树和B+树都可用于文件的索引结构

C.B树和B+树都能有效地支持顺序检索

D.B树和B+树都有效地支持随机检索

答案

参考答案:C

解析:
B树只适用于随机检索,不适用于顺序检索;而B+树把所有关键码都存在叶节点上,这就为顺序检索也提供了方便。

阅读理解

阅读短文,判断正(T)误(F)。

      I have been a news reporter for the past fifteen years. The job has taught me many unforgettable lessons. I

have seen wars, poverty and death, but I have also seen courage (勇气), hope and happiness.

      In India, I saw many homeless children. Some were as young as four year old. They lived in the streets

begging (乞讨) or stealing. But then a wonderful lady called Rosa opened a home for them. Within one year she

was looking after two hundred children. She clothed them, fed them and taught them. She gave them hope.

      Another time, I was in Turkey after a terrible earthquake. I found an old lady whose house was broke down.

Her son was missing and people said there was no chance that he was still alive. But the lady did not give up

hope. For four days, she moved heavy stones one at a time. She did not stop until she found her son. He was

alive.

      Here in China, I was surprised when I met a young boy who had had twenty operations and spent nearly his

whole life in hospital. I thought he would be sad, but when I met him, his smile was so warm and welcoming.

      In life, we need models that we can learn from. When my life is difficult, I try to remember the courage and

goodness of these three people.

( ) 1. The underlined word "poverty" probably means the state of being poor.

( ) 2. A man was looking after two hundred children.

( ) 3. The old lady's son was saved by some people.

( ) 4. The speaker was surprised while meeting the sick boy because he was in hospital all his life.

( ) 5. The main purpose of the speaker is to ask people to live with hope and courage.

单项选择题