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 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 faults 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 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.
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

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

Which of the following can be the best 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