Do you know how to keep food fresh?
　　We all know that food will 1. ______(easy)go bad if they get too warm.So we usually put them into our refrigerators to keep 2.c______ in hot weather.But can you make it without refrigerators? In 1995, Abba, a teacher from Nigeria, 3. ______(find) a cool way.His 4. ______(发明) was called Pot-in-Pot Cooling System.It uses two clay pots (陶罐).There is a 5. ______(small) pot inside a larger one.There must be some space.The space between the two pots is filled 6. ______ wet sand.Fruit, vegetables or drinks can be put into the smaller pot.A wet cloth 7. ______ (cover) the whole cooling system.Some food can be kept fresh several 8. ______ (week) in it.Abba built five thousand pot-in-pot systems for the families in his hometown.Then people all 9. ______ the country began using the invention.Soon it became 10.p______ with farmers in other African countries.In 2000,Abba got a prize-the Rolex Award.If you are trying to do something to improve human life, you may have the chance to get this prize. Why not have a try?