[单项选择]

A well-documented body of information exists showing that noise can affect human in both physiological and psychological ways.
Hearing losses in particular occupations such as boiler-making and construction work are well known. In fact, however, we all find hearing more difficult as we age. Young ears can distinguish a wide range of sounds from low to very high frequencies, while older ears lose the ability to distinguish high-pitched sounds. A comparison of some industrialized versus non-industrialized people suggests that this hearing loss may not be the must-be result of old age.
Furthermore, a closer examination of other data reveals economic effects. For instance, airports are currently operating at less capacity because of noise regulations which restrict their hours of operation. Job performance can be seriously affected by loud noise, especially if accuracy and mental effort are involved. The use of outdoor areas for conversation is not possible for an est
A. have to operate for a longer time
B. cannot operate any longer
C. have to reduce their operation hours
D. have to close earlier than usual

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