Sunbath and SkinCancer

In thesummer,millions of Americans will offer up their bodies to the sun rays.A tanmndi-cates health and beauty,and most sun worshippers will sacrifice a lot toachieve

it,includingthemselves.

With each hour, thesun's ultraviolet radiation (紫外线）produces irreversible（不可逆的） damage,hasteningthe development of unsightly wrinkles.And with each year

on the beach orroof-top,the sunbather increases his risk of getting skin cancer. Skin canceris by far the most common form of cancer. An estimated 400,000 new cases will

be detected thisyear in the United States,and almost all of them can be blamed on over-exposure to the sun.

Fortunately,most ofthese cancers are highly curable .But they can he disfiguring and take time totreat. For that reason,sun worshippers should treat deity with a good deal of

awe（敬畏）. Sunburn,of course,is the initialhazard posed by UV radiation.Prolonged exposure to UV,howev-er , interfereswith the production of collagen fibers（胶原纤

维）in thedermis（真皮层）, causing the skin to lose elasticity（弹性）and creating premature wrinkles. Further deterioration（恶化）of the dermis deprives the

epidermis（表皮层）of nutrition and causes it tobecome thin and dry.

Cancer is UV's finalresult.Shortwave radiant energy,especially from the UV-B band,breaks thestrands（股、缕）of DNA.Enzymes（酶）work constantly to rearrange the

DNA into properSe-quence,but with repeated UV exposure,the repair process may eventually breakdown.Then the mutant（变异的）DNAmay produce a colony of cancer

cells. But skincancer may be avoided with a good dose of common sense.People with fair skinand blue eyes who burn easily stand the high-est risk .Special danger spots are

the parts of thebody most constantly exposed to the sun,such as the cheeks , nose , lower lipand the ears. People who have already developed precancerous（癌变前的）

lesions（伤害）or had one skin-cancer growth standa greatly increased chance of developing others.

Dermatologists（皮肤科医生）recommend avoiding the sun whenit is most intense between 11 a.m.and 3 p.m.Anyone who insists on sunbathingshould use a good sun

screen.These lotionsand salves（药膏）containchemicals that block out the burning UVB radiation while permitting the tanningrays to reach the skin.What may be theworst result after the repair process of the DNA finally fail?

A.Shortwave radiantenergy breaks the strands of the DN

B.The mutant DNA mayproduce a colony of cancer cells.

C. Enzymes work torearrange the DNA into a new order.

D.The patient isexposed to UV from time to time.