题目内容：
根据以下内容回答题：A well-documented body of information existing shows that noise call 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 heating more difficult as our 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 peoples 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 accu-racy and mental effort are involved．The use of outdoor areas for conversation is not possible for an estimated 5 to 10 million people who live or work in urban areas．When interference with television or speech or sleep is included，as many as 22 to 44 miHion people cab be said to have lost part of the use of their homes and grounds because of noise．Thus noise pollution is a serious environmental concern．Much more effort should be made to waru people of the grave effects which may stop from an excessively noisy environment．
Boiler-making and construction work are given as examples of__________ ． A．noisy and hearing-affecting working environment
B．successful control of noise pollution
C．noise of very low or high frequencies
D．sources of high-pitched sound
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