Farmer Ed Rawlings smiles as he looks at his orange trees. The young oranges are growing well in Florida's weather. Warm sunshine and gentle rains, along with Ed Rawlings' expert care, will produce a good crop of oranges this year.
　　But Ed has to fight against Florida's changeable winter weather. In January and February, temperatures can destroy Ed's entire orange, crop. Having farmed in Florida for the past 35 years, Ed Rawlings is prepared for the frosts(霜). When temperatures drop below freezing， Ed tries to save his crop by watering his orange trees. The water freezes and forms a thin layer (层)of ice on the trees. Strange as it may sound, this thin layer of ice actually keeps the fruit warm.
　　What happens is simple. When the trees are watered, the water loses heat and becomes ice. The warmth of the heat it loses is sucked in by the fruit and keeps its temperature at a safe level. Ed Rawlings has effectively used this method(方法)to save many orange crops.
　　But Ed still faces some difficulties. The trees should be watered at the exact moment the temperature drops to the freezing point. Also, just the right quantity of water must be used. Too much water can form a thick layer of ice that will break the trees' branches. Another difficulty is that wind blows away the heat. So Ed has to worry about not only when but also how often his trees should be watered, and how much water should be used.
　　Computer technology may help Ed Rawlings with some of these worries. With equipment, air and soil temperatures and wind speed can be measured. The information is fed into a computer which can tell when temperatures drop to freezing. The computer can correctly decide the quantity of water to be used and how frequently the trees should be watered. Ed Rawlings will find looking after his orange trees a lot easier with the help of a computer, and we'll all have the benefits(or advantages)of computer-age oranges.
1. The passage is mainly about _____ .
A.a farmer's expert care for his orange trees 
B. the different uses of computers
　C. growing oranges in Florida's changeable weather
　D. different ways of frost protection
2. Ed tried to protect his crop by _____ .
　A. using a wind machine to drive away the cold air
　B. equipping his orange trees with a computer
C. watering it at the proper time 
D. picking his fruit at the first sign of frost
3. In the writer's eyes, computers _____ .
A.are too expensive for small farmers
B. can be a valuable tool for the farmer
　C. can be used to help oranges grow bigger    
　D. cannot take the place of the farmer's experience and judgement
4. Which of the following is NOT NECESSARY for Ed Rawlings to do?
　　A. He should water the orange trees as soon as the temperature drops to the
　　　 freezing point.
　　B. He should decide the quantity of water for the orange trees.
　　C. He has to water the orange trees more often in January and February.
　　D. He has to judge how often he should water the orange trees.
5. According to the passage, the computer technology can _____ .
A.get rid of the need for frost protection 
B. help the farmer get a better harvest
　C. tell the farmer why outdoor temperature changes
D. prevent the temperature from dropping to the freezing point