阅读理解
A new study has found no evidence that sunscreen, commonly used to reduce the risk of skin cancer, actually increase the risk.
Researchers from the University of Iowa 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 has been raised about sunscreen and whether it may has 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(白皙的肤色) 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. evidence
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 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
(合并及居中)按钮。 ③选择“B3:B6”单元格，单击“常用”工具栏中的
(自动求和)按钮；选择C3单元格，在编辑栏中输入“=B3/$B$6”，单击编辑栏中的(输入)按钮；然后单击C3单元格，将鼠标指针指向该单元格右下角的填充句柄，使其形状由空心的十字形变为黑色的十字形，按住鼠标左键，拖动单元格填充句柄至C5单元格。 ④双击工作表Sheet1文件名，输入新的工作表名“学生人数情况表”。 ⑤选择工作表的“A2:A5”单元格，按住＜Ctrl＞键，再选择“C2:C5”单元格，单击“常用”工具栏中的
(图表向导)按钮，弹出“图表向导-4步骤之1-图表类型”对话框。在“标准类型”选项卡中，“图表类型”选择“饼图”，“子图表类型”选择“饼图”，单击“下一步”按钮，弹出“图表向导-4步骤之2-图表源数据”对话框。接受默认设置，并单击“下一步”按钮，弹出“图表向导-4步骤之3-图表选项”对话框。在“标题”选项卡中，“图表标题”输入“学生人数年级比例图”，单击“下一步”按钮，弹出“图表向导-4步骤之4-图表位置”对话框。点选“作为其中的对象插入”单选钮，单击“完成”按钮，即可在工作表中插入图表。利用鼠标光标调整图表大小到“A9:F19”单元格区域内。 ⑥设置完成后，执行“文件”→“另存为”菜单命令，弹出“另存为”对话框。输入保存的地址，单击“保存”按钮。