6．Every time we turn on the TV or take a ride in a car，we could be adding to a problem called acid rain（酸雨）．In this article，we'll learn something important about acid rain． The formation of acid rain When people use fuels （燃料），such as coal and gasoline（汽油），poiso nous gases are given off．When these gases come together with rain，acid rain forms．Many power stations burn fuels in order to create the electricity（電） that we use in our homes and offices every day．Cars and trucks also send these gases into the air when they burn gasoline．When rain meets these gases，harmful things called acids form．This is acid rain． The harm of acid rain Acid rain destroys everything that it touches．It poisons our rivers，ponds and lakes and oceans along with the life in them．It pollutes our soils and crops，harm trees，and can even kill fish and plants．Acid rain also eats away at our buildings． The prevention of acid rain We need to reduce and even stop the pollution that gets into our air．Turn off lights，televisions and other electrical appliances（電器） if we are not using them．Walk and take a bike whenever possible．If we are travelling a long distance，take a bus or train to save fuel． As research shows，acid rain harms our environment．But people everywhere can take small steps now to help protect our environment for future generations． Whenever we use electricity or drive our cars we may add something bad to the air around us．And even worse，we may cause a terrible problem-acid rain． The formation of acid rainWhen fuels，such as c oal and gasoline are burnt，harmful gases are sent into the air．When these gases （1）mixwith rain，acid rain forms． The harm of acid rainAcid rain is greatly （2）harmful to the environment．It makes our rivers，ponds and lakes and oceans dirty and （3）causs the death of fish and plants．And it can corrode （腐蝕） the buildings we live in． The prevention of acid rain Trying to prevent the pollution that gets into the air is（4）necessary．Keep the electrical appliances off while they are not in use．We can also use different ways of traffic to make less use of fuels． Research tells us that acid rain harms our environment．So people around the world can take small steps now to make a （5）differenceto our kids．
7．In many countries，people travel （61）by car or by bike．They also get from place to place using popular （62）transport such as buses and trains．However，some people live in parts of the world where it is impossible （63）to build roads．In these places，animals or other facility （64）of transport have to be used． It is difficult to walk （65）in snow but easy to ski over it．So in places like Alaska，people use skis．If they want to go faster，they get dogs to pull （66）them on sleds（雪橇）．Riding a snowmobile（雪地摩托） is a more modern （67），but expensive way of getting around on snow． In desert（沙漠） like the Sahara in North Africa，people sometimes （668）get around on camels．Camels survive well （9）in the desert，not because they can save （70）water in their bodies though!They can survive without water for two weeks and without food （71）for up to a month．He （72）can only go without water for about three to five days．
