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.

　　16. 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

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

　　A. fronts

　　B. thermal changes C. Frost

　　D. wind speed

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

　　A. daily weather maps B. upper air levels C. satellite reports D. changing fronts

　　19. 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

　　20. Artificial rainmaking has been most successful in the_______.

　　A. lake area

　　B. western slope of mountains

　　C. grass lands

　　D. windward side of mountains

　　Passage Five

　　Questions 21 to 25 are based on the following passage

　　There are two types of people in the world.Although they have equal degree of health and wealth and other comforts of life, one becomes happy, while the other becomes unhappy.This arises from the different ways in which they consider things, persons, events and the resulting effects upon their minds.

　　People who are to be happy fix their attention on the convenience of things: the pleasant parts of conversation, the well prepared dishes, the goodness of the wine and the fine weather.They enjoy all the cheerful things.Those who are to be unhappy think and speak only of the opposite things.Therefore, they are continually dissatisfied.By their remarks, they sour the pleasure of society, offend(hurt) many people, and make themselves disagreeable everywhere.If this turn of mind was founded in nature, such unhappy persons would be the more to be pitied.The intention of ccriticizing and being disliked is perhaps taken up by imitation.It grows into a habit, unknown to its possessors.The habit may be strong, but it may be cured when those who have it realize its bad effects on their interests and tastes.I hope this little warning may be of service to them, and help them change this habit.