托福听力
44-46 Listen to part of a radio program about environmental issues． Our electric car is the way of the future．Automobile manufactures are under the pressure to develop cars that do not pollute．One powerful motive is a California law requiring that by the year 2000 10％of the new car sales in the state be so-called zero emission vehicles．These cars must put no pollutants whatsoever into the atmosphere．California is a huge market for the automobile companies．So they are working hard to meet these standards．So far the electric Car seems to be the best alternative．So the biggest advantage of electric cars is that they don’t pollute．However they will be in competition with gas powered cars．And that’s where the weaknesses come out．The big problem is that the batteries in electric cars weigh a lot relative to the amount of power they deliver．For instance in one electric car the batteries weigh four hundred kilograms and they provide enough energy to go 250 km before recharging，which take 8 hours．Compare that to a moderately fuel efficient conventional car it can go 400--700 km on a tank of gas．And refilling takes just minutes．If there are other drains on an electric car’s batteries besides a motor，headlights，air-conditioning or a heater，its already limited range would be significantly reduced．So automobile engineers are trying to make more powerful batteries that would increase the car’s range and make them more attractive to buyers