Life gets noisier every day and very few people can be free from noise of some kind or another. No matter where you live--in the middle of a modern city or a far-away village--the chances are that you will be disturbed by jet planes, transistor radios, oil-powered engines, etc. We seem to be getting used to noise, too. Some people feel quite lonely without background music while they are working.

　　Scientific tests have shown that total silence can be a very frightening experience for a human being. However, some people enjoy listening to pop music which is very loud, and this can do harm to their eardrums（耳膜）. The noise level in some discos is far above the usual safety level for heavy industrial areas.

　　One recent report about noise and concentra-tion（注意力）suggested that although a lot of people say that any noise disturbs their concent-ration, what really influences the ability to concentrate is a change in the level of noise. It goes on to say that a background noise which doesn't change too much（music, for example）may even help to concentrate.

(1)According to this passage, the noise pollution ________.

[　　]

A．has become the worst in the country-side

B．has become better in big cities

C．has spread from cities to villages

D．has been controlled in modern cities

(2)Some people have their hearing harmed ________.

[　　]

A．while listening to very loud pop music

B．in complete silence

C．when speaking loudly

D．while watching TV

(3)Which of the following isn't included among the things causing noise?

[　　]

A．Bicycles.

B．Motorcycles.

C．Electric engines.

D．Jet planes.

(4)Scientists have discovered that what prevents people from concentrating on something is ________.

[　　]

A．all kinds of noise

B．changes in the level of noise

C．background noise

D．popular music