【正文】 etermi ned. Every tim e you feel li ke sm oki ng a cigarette, rem i nd yoursel f that you are a nonsm oker. Reread the li st of benefi ts you wrote earl i er. Break the habi t. Instead of sm oki ng a ci garette, do som ethi ng el se. Go for a wal k, cl ean your teeth, dri nk som e water, cl ean the house。 crops wil l produce m ore。 that i s, the part of the body that fi ghts di sease. You can have H IV i n your bl od for a l ong tim e, but eventual y H IV wi l dam age your i mm une system so m uch that your body can no l onger fight di sease. Thi s stage of the il l ness i s cal ed AIDS. If you devel op AIDS, your chances of survi val are very sm al l. H IV i s spread through bl ood or the fl ui d that the body m akes duri ng sex. For a person to be e i nfected, bl ood or sexual flui d that carri es the virus, has to get i nsi de the body through broken ski n or by i njecti on. O ne day sci enti sts wil fi nd a cure for H IV/AIDS. Until that happens, you need to protect yoursel f. H ere are som e thi ngs you can do to m ake sure you stay safe. If you i nject drugs: do not share your needl e wi th anyone el se. Bl ood from another person can stay on or i n the needl e. If a person has H IV and you use the sam e needle, you coul d inject the virus i nto your own bl ood. do not share anythi ng el se that a person has used whil e i njecti ng drugs. Blood coul d have spi l t on i t. If you have sex wi th a m al e or a femal e: use a condom. This wi l prevent sexual fl ui d passi ng from one person to another. The fol owi ng statem ents are NOT true. A person cannot get H IV the fi rst tim e they have sex. WRO N G. If one sexual partner has H IV, the other partner coul d be e i nfected. You can tel l by l ooki ng at someone whether or not they have H IV. WRON G. Many peopl e caryi ng H IV l ook perfectl y heal thy. It i s onl y when the di sease has progressed to AIDS that a person begi ns to l ok si ck. Onl y hom osexual s get AIDS. WRON G. Anyone who has sex with a person i nfected wi th H IV/AIDS ri sks getti ng the vi rus. Women are sli ghtly m ore li kel y to be e infected than m en. If you hug, touch or ki s som eone with AIDS or vi si t them i n thei r hom e, you wil l get H IV/AIDS. WRON G. You can only get the disease from bl ood or sexual fl ui d. Unfortunatel y, peopl e wi th HIV som etim es l ose thei r friends because of prejudi ce. Many peopl e are afrai d that they wi l get H IV/AIDS from those i nfected wi th H IV/AIDS. For the sam e reason, som e AIDS pati ents cannot fi nd anyone to l ook after them when they are si ck. You can get H IV/AIDS from m osqui toes. WRON G. There i s no evi dence of thi s. Uni t 4 TH E EARTH IS BECO MIN G WARMER BUT DO ES IT MATTER? Duri ng the 20th century the tem perature of the earth rose about one degree Fahrenhei t. That probabl y does not seem m uch to you or m e, but i t i s a rapi d i ncrease when pared to other natural changes. So how has this e about and does i t m atter? Earth Care?s Sophi e Arm strong expl ores these questi ons. There i s no doubt that the earth i s be i ng warm er (see Graph 1) and that is i t hum an acti vi ty that has caused thi s gl obal warmi ng rather than a random but natural phenom enon. Al l sci enti sts subscri be to the vi ew that the i ncrease i n the earth?s tem perature i s due to the burni ng of fosil fuel s li ke coal , natural gas and oil to produce energy. Som e byproducts of thi s proces are cal ed “greenhouse” gases, the m ost im portant one of whi ch i s carbon di oxi de. Dr Jani ce Foster expl ai ns: “There i s a natural phenom enon that sci enti sts cal the ?greenhouse effect?. Thi s i s when sm al l am ounts of gases in the atm osphere, li ke carbon dioxi de, m ethane and water vapor, trap heat from the sun and therefore warm the earth. Wi thout the ?greenhouse effect?, the earth woul d be about thi rtythree degrees Cel sius cool er than i t i s. So, we need those gases. The probl em begi ns when we add huge quanti ti es of extra carbon di oxi de i nto the atm osphere. It m eans that m ore heat energy tends to be trapped i n the atmosphere causi ng the gl obal tem perature to go up. ” We know that the l evel s of carbon di oxi de have i ncreased greatly over the l ast 100 to 150 years. It was a sci enti st cal l ed Charl es Keeli ng, who m ade accurate measurem ents of the am ount of carbon di oxi de i n the atm osphere from 1957 to 1997. H e found that between these years the carbon di oxi de in the atm osphere went up from around 315 parts to around 370 parts per m il i on (see Graph 2). Al l sci enti sts accept thi s data. They al so agree that it i s the burning of m ore and m ore fossil fuels that has resulted i n thi s increase in carbon di oxi de. So how hi gh wi l the tem perature increase go? Dr Jani ce Foster says that over the next 100 years the am ount of warmi ng coul d be as l ow as 1 to 1. 5 degrees Celsi us, but i t coul d be as hi gh as 5 degrees. H owever, the atti tudes of sci entists towards thi s ri se are pl etel y di fferent. O n the one hand, Dr Foster thi nks that the t rend whi ch i ncreases the tem perature by 5 degrees woul d be a catastrophe. She says, “We can?t predict the cl im ate wel l enough to know what to expect, but it coul d be very seri ous.” O thers who agree with her thi nk there may be a ri se of several m etres in the sea l evel, or predi ct severe storm s, fl oods, droughts, fami nes, the spread of diseases and the di sapearance of speci es. O n the other hand, there are those, li ke Gee H am bl ey, who are opposed to thi s vi ew and bel i eve that we shoul d not worry about hi gh l evel s of carbon di oxi de i n the ai r. They predi ct that any warm i ng will be mi l d with few bad environm ental consequences. In fact, H am bl ey states, ” More carbon di oxi de i s actual l y a positi ve thi ng. It wil l m ake pl ants grow qui cker