Since the energy is available only during the day and only then when there is not a great deal of cloud cover, the heat must be stored. This can be done in wa¬ter, or in rock or pebble beds. The energy is stored in the hot water in the pipes.

　　21. Solar energy was first used_______.

　　A. to start a fire B. to cook food

　　C. to power a heating-system D. in a war

　　22. What must be done to solar energy before it can be used?

　　A. It must be stored in rock beds. B. It must be distilled.

　　C. It must be converted to heat. D. It must be purified.

　　23. There is so much research into the use of solar energy because '_______.

　　A. more irrigation projects are needed B. the construction industry is expanding C. fossil fuels are running out D. it transmits electromagnetic radiation

　　24. Solar energy must be stored because_______.

　　A. it is limited B. there is not much of it

　　C. it is not always available D. the passage does not tell us why

　　25. How many uses has solar energy been put to according to the passage? A. 2. B. 3.

　　C. 4. D. More than 4.

　　21. D 22. C 23. C 24. C 25. B

　　A weather map is an important tool for geographers. A succession of three or four maps presents a continuous picture of weather changes. Weather forecasters are able to determine the speed of air masses and fronts; to determine whether an individual pressure area is deepening or becoming shallow and whether a front is increasing or decreasing in intensity. They are also able to determine whether an air mass is retaining its original characteristics or taking on those of the surface over which it is moving. Thus, a most significant function of the map is to reveal a synoptic picture of conditions in the atmosphere at a given time.

　　All students of geography should be able to interpret a weather map accurately. Weather maps contain an enormous amount of information about weather condition existing at the time of observation over a large geographical area. They reveal in a few minutes what otherwise would take hours to describe. The United States Weather Bureau issues information about approaching storms, floods, frosts and all climatic conditions in general. Twice a month it issues a 30-day "out-look" which is a rough guide to weather conditions likely to occur over broad areas of the United States. These 30-day outlooks are based upon an analysis of the upper air levels which often set the stage for the development of air masses, fronts, and storms.

　　Considerable effort is being exerted today to achieve more accurate weather predictions. With the use of electronic instruments and earth satellites, enormous gains have taken place recently in identifying and tracking storms over regions which have but few meteorological stations. Extensive experiments are also in progress for weather modification studies. But the limitations of weather modification have prevented meteorological results except in the seeding of super¬cooled, upslope mountainous winds which have produced additional rainfall on the windward side of mountain ranges. Nevertheless, they have provided a clearer understanding of the fundamentals of weather elements.

　　26. The observation of weather conditions by satellites is advantageous because it_______.

　　A. enables man to alter the weather

　　B. makes weather prediction easier

　　C. gives the scientist information not obtained readily otherwise

　　D. uses electronic instruments

　　27. One characteristic of weather maps NOT mentioned by the author in this passage is

　　A. fronts B. thermal changes

　　C. frost D. wind speed

　　28. The thirty-day forecast is determined by examining_______.

　　A. daily weather maps B. upper air levels

　　C. satellite reports D. changing fronts

　　29. At the present time, experiments are being conducted in_____

　　A. 30-day "outlook" B. controlling storms

　　C. controlling weather D. determining density of pressure groups

　　30. Artificial rainmaking has been most successful in the_______.

　　A. lake area B. western slope of mountains

　　C. grass lands D. windward side of mountains

　　26. C 27. B 28. B 29. C 30. D