问题 单项选择题

最简单的交换排序方法是( )。

A.快速排序

B.选择排序

C.堆排序

D.冒泡排序

答案

参考答案:D

解析: 所谓的交换排序方法是指借助数据元素之间的互相交换进行排序的一种方法,包括冒泡排序和快速排序。冒泡排序是一种最简单的交换排序方法,它通过相邻元素的交换,逐步将线性表变成有序。

选择题
阅读理解

阅读理解。

     A new study has found no evidence that sunscreen, commonly used to reduce the risk of skin cancer,

actually increases the risk.

     Researchers from the University of lows based their findings on a review of 18 earlier studies that looked

at the association between sunscreen use and melanoma (黑素瘤). They said that they found flaws in studies

that had reported associations between sunscreen use and higher risk of melanoma.

     Most health experts believe that by protecting the skin from the harmful effects of the sun, sunscreen

helps prevent skin cancer, which is increasing in incidence (发生率) faster than any other cancer in the

United States.

     But questions have been raised about sunscreen and whether it may have the opposite effect, perhaps

by allowing people to remain exposed to the sun longer without burning.

     The researchers said that among the problems with some earlier studies is that they often failed to take

into account that those people most at risk for skin cancer-people with fair skin and freckles (雀斑), for

example-are more likely to use sunscreen. As a result, it may appear that sunscreen users get cancer more

often.

     The studies, which generally relied on volunteers to recall their sunscreen use, were also unable to prove

how well the products had been applied, said the new study.

1. The underlined word "flaws" in the 2nd paragraph most probably means _____.

A. evidences

B. facts

C. faults

D. failures

2. People with fair skin and freckles _____.

A. seldom use sunscreen

B. are more in danger of skin cancer

C. can be free from the harm of the sun

D. often expose themselves to the sun

3. We can learn from the passage that _____.

A. sunscreen users get skin cancer more often

B. the volunteers have proved the effect of sunscreen

C. the new study was based on the experiences of volunteers

D. the number of skin cancer patients is increasing in America

4. Which of the following can be the beat title for this passage?

A. Sunscreen to Prevent Skin Cancer

B. Sunscreen to Increase Skin Cancer

C. Skin Cancer Caused by Sunscreen

D. Skin Cancer Caused by Freckles