People build many different kinds of shelter throughout the worlD.The types ofshelters they erect depend   16   on the climate and on what building materials are  17  .In hot areas, the weather is warm enough for people to live   18  much ofthe time. But they still need protection  19  sun, rain, and insects. Houses there have many screened windows, doors, and other openings that let in breezes but keep out insect pests. In the cool regions, houses are   20  to keep out the cold and keep in heat. Many buildings have thick walls to   21  heat loss. In such snowy countries as Norway and Sweden, people build houses with sloping roofs   22   snow will slide off easily.Building methods and materials   23  widely throughout the worlD.In regionswith large forests, many people use wood to build homes.   24  is easy to build with, but most wooden buildings are less sturdy than those made of stone or concrete.In areas with little  25  , people construct many shelters of clay or muD.InMexico and the southwestern United States, for example, people   26  clay and dirt or mud with water to make adobe (砖坯). In wet tropical areas,   27   causes wood shelters to rot within a few years. People in these areas build houses from other materials. For example, in some parts of Africa and on many Pacific islands, people weave the   28  of tall grass into houses.High-rise buildings made of steel and concrete are most common in suchindustrial countries as the United States and Canada. Prefabricated buildings  29   parts manufactured at a factory and then shipped to the construction   30   . There construction workers assemble the parts. Many prefabricated shelters use large amounts of plastic and other lightweight materials.

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