单项选择题：某班有50名学生，考试后老师想迅速计算出所有学生的平均分，可以使用的函数是（）A、M

题型：单项选择题

Water problems in the future will become more intense and more complex. Our increasing population will tremendously increase urban wastes, primarily sewage. On the other hand, increasing demands for water will decrease substantially the amount of water available for diluting wastes. Rapidly expanding industries which involve more and more complex chemical processes will produce larger volumes of liquid wastes, and many of these will contain chemicals which are noxious. To feed our rapidly expanding population, agriculture will have to be intensified. This will involve ever - increasing quantities of agricultural chemicals. From this, it is apparent that drastic steps must be taken immediately to develop corrective measures for the pollution problem.

There are two ways by which this pollution problem can be dwindled(减少). The first relates to the treatment of wastes to decrease their pollution hazard . This involves the processing of solid wastes "prior to" disposal and the treatment of liquid wastes, or effluents, to permit the reuse of the water or minimize pollution upon final disposal .

A second approach is to develop an economic use for all or a part of the wastes. Farm manure is spread in fields as a nutrient or organic supplement. Effluents from sewage disposal plants are used in some areas both for irrigation and for the nutrients contained. Effluents from other processing plants may also be used as a supplemental source of water. Many industries, such as meat and poultry processing plants, are currently converting former waste products into marketable byproducts. Other industries are potential economic uses for waste products.

小题1:The purpose of this passage is ________.

A．to alert the reader to the dwindling water supply

B．to explain industrial uses of water

C．to acquaint the reader with water pollution problems

D．to demonstrate various measures to solve the pollution problem小题2:Which of the following points is NOT included in the passage?

A．Industrial development includes the simplification of complex chemical processes.

B．Diluting wastes needs certain amount of water.

C．Demands for water will go up along with the expanding population .

D．Intensive cultivation of land require more and more chemicals.小题3:The reader can conclude that _________.

A．countries of the world will work together on pollution problems

B．byproducts from wastes lead to a more prosperous marketplace

C．science is making great progress in increasing water supplies

D．some industries are now making economic use of wastes小题4:The author gives substance to the passage through the use of________.

A．interviews with authorities in the field of water controls

B．opinions and personal observations

C．definitions which clarify important terms

D．strong arguments and persuasions小题5:The underlined words "prior to"(para. 2)probably man________.

A．after

B．during

C．before

D．beyond

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某班有50名学生，考试后老师想迅速计算出所有学生的平均分，可以使用的函数是（）A、M

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