Life gets noisier every day and very few people can be free from noise of some sort or another. It doesn’t matter where you live ---- in the middle of a modern city, or a faraway village --- the chances are that you’ll 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’re 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 (耳鼓). The noise level in some discos is far above the usual safety level for heavy industrial areas.
One recent report about noise and concentration suggested that although a lot of people say that any noise disturbs their concentration, what really influences their 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.
According to this passage, the noise pollution ____________________.

A．has become the worst in the countryside

B．has become better in big cities

C．has spread from cities to villages

D．has been controlled in modern cities

Some people have their hearing harmed _____________.

A．while listening to pop music

B．in complete silence

C．when speaking loudly

D．while watching TV

Which of the following isn’t included among the things causing noise?

A．trucks	B．motorcycles
C．electric engines	D．jet planes

Scientists have discovered that what prevents people from concentrating on something is _______.

A．all kinds of noise	B．great changes in the level of noise
C．background noise	D．popular music