The problem to be taken up and the point at which the search for a solution will begin are customarily prescribed by the investigator (1) a subject participating in an (2) on thinking (or by the programmer for a computer). (3) , prevailing techniques of (4) in the psychology of thinking have invited (5) of the motivational aspects of thinking. The conditions that determine when the person will begin to think in (6) to some other activity, what he will think about, what direction his thinking will take, and when he will regard his search for a solution as successfully terminated (or abandon it as not worth pursuing further) (7) are beginning to attract investigation. (8) much thinking is aimed at (9) ends, special motivational problems are raised by "disinterested" thinking, in which the (10) of an answer to a question is a source of satisfaction in itself.
For computer specialists, the detecti
A. Although
B. Since
C. Unless
D. Provided
It may be necessary, in order that future (51) can enjoy clean air, that more of the (52) is borne by long-term central government fund. As air pollution varies enormously from place to place and can, indeed, be very local, it may also be necessary for the central government to (53) money so that local authorities can (54) special local problems. That these can be significant was shown by the report made in 1970 (55) behalf of the London Boroughs Association. This (56) that in central London since 1958 smoke concentrations have decreased by 80 percent, whereas sunshine has increased by 70 percent and winter visibility has (57) threefold. There have been (58) in mortality and hospital admissions (59) with air pollution and in the response to it of bronchitis, as well as clear if less documented increases in plant types and bird (60) in the cities.
57（ ）.
某企业在五年前就准备购建一条生产线，并已经做了前期调查和可行性分析，支付相关费用10万元。但由于资金没有落实，该项目被搁置下来。现在已经筹集到该项目所需要的资金，企业重提旧事。
该生产线购置费1500万元，预计可使用10年，预计每年将发生维护修理费用 10万元，预计报废时可得净残值收入30万元，同时该生产线需要追加配套的流动资金200万元。生产线投产后，估计每年扣除付现成本后的营业收入为400万元。企业的资本成本为5%。
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