[单项选择]

Psychologists now believe that noise has a considerable effect on people’s attitudes and behavior. Experiments have proved that in noisy situations (even temporary ones ), people behave more irritably and less cooperatively; in more permanent noisy situations, many people cannot work hard, and they suffer from severe anxiety as well as other psychologecal problems. However psychologists distinguish between“sound”and “noise”.“Sound”is measured physically in decibels.“Noise”cannot be measured in the same way because it refers to the psychological effect of sound and its level of “intensity”depends on the situation. Thus, for passengers at an airport who expect to hear airplanes taking off and landing, there may be a lot of sound, but not much noise (that is, they are not botered by the noise). By contrast, if you are at a concert and two people behind you are whispering you feel they are talking noisily even if there
A. enjoy hearing airplanes taking off and landing
B. are. usually not troubled by the noise
C. can easily tell sound from noise
D. are often physically affected by the noise