题目：
B
A new study has found no evidence that sunscreen, commonly used to reduce the risk of skin cancer, actually increases the risk.
Research 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 have been raised about sunscreen and whether it may have the opposite effect 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---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.
60．The underlined word “flaws” in the 2nd paragraph most probably means _________.
A．evidences B．facts C．faults D．failures
61．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
62．We can learn from the passage that _________.
A．sunscreen users get skin cancer more often
B．the volunteers have proved the effect of the sunscreen
C．the new study has based on the experiences of volunteers
D．the number of skin cancer patients is increasing in America
63．Which of the following is the best title of the 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
答案：
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答案：B题目分析：盐酸易挥发，所以生成的CO2中除了含有水蒸气以外，还有氯化氢气体。首先要除去氯化氢，利用饱和的碳酸氢钠溶液，最后通过浓硫酸干燥即可，答案选B。2制备中除杂的有关判断点评：该题是基础性试...
