[audioFiles]audio_ezf_m_0229(20102)[/audioFiles]

游客2024-10-27  8

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答案                                               Keep Food Cool
     Bacteria can make foods go bad./ This is true of cooked foods as well as fresh foods./ The problem is especially dangerous when the air around food is warm./ High heat kills bacteria./ But warm, wet conditions help bacteria grow./
     So, the best way to protect food is to keep it in a cool place./ There are several ways to keep food cool without the need for electricity./ Some refrigerators, for example, are powered by gasoline motors./
     There are less costly ways than refrigeration to keep food cool./ An ice box is a simple device./ It is made mostly of wood./ The inside walls are covered with metal./ A big piece of ice is placed in the bottom./ Millions of homes had ice boxes/ until refrigerators became common in the 1940s./
     An ice box will keep food from spoiling for several days/ if the outside temperature is not too warm./ If the box is kept out of sunlight, the ice will last longer./
     Probably the best method to keep food cool without electricity/ is a device called the evaporative cooler./ Evaporation is the natural change of water from liquid to gas/ as the water mixes back into the atmosphere./ An evaporative cooler is easy to make. And it does not need ice./

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