2. 外语
  3. One reason human beings can thrive in all kinds of climates is that they can control the qualities of the air in the enclosed sp

One reason human beings can thrive in all kinds of climates is that they can control the qualities of the air in the enclosed sp

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问题       One reason human beings can thrive in all kinds of climates is that they can control the qualities of the air in the enclosed spaces in which they live. Air conditioning is the use of mechanical systems to 【C1】______  that control in such places 【C2】______  homes, offices, theaters, institutions, factories, airplanes, and automobiles. The most familiar type of air conditioning is summertime cooling., Although important, this is 【C3】______  one of several aspects of air conditioning. Other applications 【C4】______  the control of the humidity (or air moisture), cleanliness, circulation of the air, and heating.
     Tests have 【C5】______  that people generally feel best 【C6】______  certain temperature, humidity, and air velocity conditions. Temperatures can 【C7】______  from 21.5°C with 70 percent relative humidity to 28°C with 30 percent relative humidity. Relative humidity is the 【C8】______ of moisture in the air 【C9】______  a specific temperature compared 【C10】______  the amount it could hold at that temperature. 【C11】______  air velocities range from 4.5 to 10.5 meters per minute. It is also desirable that an air conditioner 【C12】______  dust, pollen, smoke, and odors from the air.
     In many industrial environments, air conditioning is essential. Most print shops, for example, 【C13】______ . constant humidity in order to control paper shrinkage and 【C14】______  the 【C15】______  operation in some processes. Libraries, especially ones With rare books, require air control to 【C16】______  the physical quality of their collections. Bakeries and the tobacco and cotton industries require high humidity 【C17】______  their products, and perishables such as fruits must be stored in cool, dry rooms. Some electronic components, drugs, and chemicals must be manufactured 【C18】______  the air is as free as possible 【C19】______  dust and other particles. Air conditioning is 【C20】______  in hospitals, especially in operating rooms.
【C14】
选项 A、ensures
B、ensure
C、ensuring
D、to ensure
答案D
解析 题型：语法题(动词不定式的承前省略)。在本句中，to control和to ensure作并列目的状语。
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