Passage One

　　Questions 56 to 60 are based on the following passage.

　　If you think a high-factor sunscreen (防晒霜) keeps you safe from harmful rays, you may be wrong. Research in this week's Nature shows that while factor 50 reduces the number of melanomas (黑瘤) and delays their occurrence, it can't prevent them. Melanomas are the most aggressive skin cancers. You have a higher risk if you have red or blond hair, fair skin, blue or green eyes, or sunburn easily, or if a close relative has had one. Melanomas are more common if you have periodic intense exposure to the sun. Other skin cance ..........