Passage Five

　　Keeping what remains of the ozone layer intact has been an international priority since 1988, when the Montreal Protocol was launched to cut down the chemicals that cause depletion. But in the meantime, individuals can launch their own offensives against extra doses of UV(ultraviolet) (紫外线的) radiation.

　　A universal weapon in this daily battle is sunglasses to protect the eyes, which can effectively cut out UV over a wide range. But what about our skin? People with very dark skin have an inbuilt sun protection factor (SPF) of 13, meaning they can stay out in the Sun 13 times longer than if unprotected, without burning from exposure to UV radiation. People with paler skins need sun blocks to create the same effect. Some evidence shows that sunburn in childhood could increase the likelihood of developing a malignant melanoma(黑肿瘤) later, so the younger the sun worshipper, the more vital the wearing of sun block.

　　But choose your product carefully. Because the damaging effects of UV-B are more obvious, sun block manufacturers have focused on this waveband until recently. So one of the problems with SPF numbers is that they do not indicate protection against UV-A. This is a serious omission, because claims that UV-B damage can be separated from “safe” UV-A tanning are unfounded.

　　The best protection from UV-A comes in sun blocks with reflective compounds such as titanium dioxide. Many preparations now also indicate UV-A protection using star ratings. Four stars indicates balanced UV-B and UV-A protection, while fewer stars indicates greater protection against UV-B than UV-A.

　　51. The first paragraph of the passage implies that ________.

　　A. the ozone layer has remained unchanged since 1988

　　B. ozone depletion increases the amount of UV radiation

　　C.UV radiation is harmful to our health

　　D.the Montreal Protocol bans the discharge of any chemicals

　　52.According to the passage, sunglasses ________.

　　A. can effectively block UV B. are harmful to people’s eyes

　　C. have very good quality  D. have a wide range of UV

　　53.Which of the following statements is TRUE?

　　A. The SPF for all people is 13.

　　B. Paler skins can be exposed to UV radiation longer than dark skins.

　　C. The SPF for paler skins is less than 13.

　　D. Children should stay in the Sun longer than adults.

　　54.Compared with UV-B, UV-A ________.

　　A. is not harmful to the eyes

　　B. can be better protected by sunglasses

　　C. is hardly noticed by manufacturers

　　D. has the same SPF numbers

　　55.The best product against UV radiation is the one ________.

　　A. with a star rating of 4 stars

　　B. with a star rating of less than 4 stars

　　C. with a star rating of more than 4 stars

　　D. made of reflective compounds

上一页  [1] [2] [3] [4] [5] [6]