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Questions 26 to 30 are based on the following passage:
Industry uses water for many different purposes. The uses are commonly divided into four categories: cooling water, process water, boiler feedwater, and sanitary and service water. Cooling water is water used only for cooling without coming into contact with the product of material being processed. Process water is water that comes into contact with material being processed. Boiler feedwater is water converted to steam. Sanitary and service water is that supplied for the personal use of the employees, for cleaning plants and equipment, and for the operation of valves and other apparatus.
About 90 percent of the water withdrawn by industry is used for cooling. Fuel?electric power plants use more cooling water than all other kinds of plants combined. One might suppose that the greatest amount of water used in the fuel?electric power production is used for boiler feedwater, but such use is dwarfed by the water needed for cooling condensers. Cooling water is also used to condense many products of oil refineries and chemical plants and to protect industrial equipment from excessive heat.
Most manufacturing plants use process water at some point in the course of their operation. In some plants the material being processed is in contact with water at almost every step in its conversion to the finished product. Water also serves as a solvent for chemicals in many chemical processes; and the food industry uses large quantities of water for cleaning, cooking, and canning vegetables and meats.
Another important use of water by industry is for disposal of its waste products. At one time, streamflows were adequate to dilute, dissolve, or carry away these wastes. However, some rivers in the United States are being progressively depleted by use and overloaded with wastes. This pollution not only upsets the delicate natural balance among plants, insects, and fish, but also poses problems of water quality for the people and industries downstream.
26．What does the passage mainly discuss?
A. Why does industry use the most water for cooling.
B. The conversion of raw material into finished products.
C. The disposal of waste products in industry.
D. Four basic categories of water used in industrial production.
27．Water used in industry to operate valves is called .
A. sanitation and service waterB. boiler feedwater
C. cooling waterD. process water
28．Which of the following is NOT mentioned as one of the functions of water used in industrial production?
A. coolingB. solvent for chemicals
C. carrier of waste productsD. cleaning
29．The greatest amount of cooling water is used in .
A. food industryB. fuel?electric power plant
C. chemical industryD. manufacturing industry
30. The word “depleted in the last paragraph most probably means .
A. used upB. pollutedC. flushedD. flooded
