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Problems Caused by Using Computers

Long hours at the screen can cause     41    (ache) eyes,     42   (blur) vision and headaches,  experts say. In fact, eyestrain surpasses even wrist pain as the top physical  ___43__ (complain) among heavy computer users. When peering into the computer screen, the eye's focusing muscle is at constant tension. Like any muscle, it feels sore when  ____44___(overload) . And when someone spends a lot of time looking at something close, the eye muscle can get  ____45___(stick) on the near-focus setting and have difficulty relaxing, leaving the person    46    (temporary) nearsighted, a condition called accommodative spasm (痉挛) that can last seconds or hours. The letters on the screen are not as clearly  ____47___(define) as on a printed page. Take a magnifying glass to your monitor and you'll see the letters. each made up of pinpoint sources of light, have no sharp edges. But those liquid crystal display (LCD) monitors, like those found on laptop computers, are    48    (easy) on the eyes be-cause they display sharper images. And studies have shown that when people are working on a computer, their rate of  ____49___ (blink) goes down by two-thirds, which can result in dry, stinging eyes. This is especially a problem for contact-lenses    50    (wear) . 

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A Thirsty World

The world is not only hungry;it is also thirsty for water. This may seem strange to you since nearly 75%of the earth's surface is     31    with water. But about 97%of this huge amount is sea-water, or salty water. Man can only drink and use the other 3%—the  ____32___ water that comes from rivers, lakes, underground, and other sources. And we cannot even use all of that, because some of it is in the form of icebergs and glaciers. Even  ____33___, some of it has been polluted.

At the moment, this small amount of fresh water is still enough for us. However, our demand for water is increasing     34    Only if we take steps to deal with this problem now can we avoid a severe worldwide water  ____35___ later on.

In addition to stopping wasting our precious water, one useful step we should take is to     36   ways of reusing it.

Today, in most large cities, water is used only     37    and it eventually returns to the sea or runs into underground storage tanks, But it is  ____38___ to pipe water that has been used to a purifying (净化) plant, There it can be filtered and treated with chemicals so that it can be used again just as if it were fresh from a spring.

But even if every large city purified and     39    its water, we still would not have enough. Where could we turn next?To the oceans!We can make use of the vast amount of sea-water by re-moving the salt. This salt-removing     40    is already in use in many parts of the world.

A. used	B. fresh	C. develop
D. process	E. possible	F. shortage
G. worse	H. reused	I. rapidly
J. covered	K. new	L. once

According to the passage, performers could best meet their obligation to composers by doing which of the following?

• A、Taking courses in art appreciation.
  
  

• B、Knowing how the music was intended to be performed.
  
  

• C、Studying works written at different periods in history.
  
  

• D、Rearranging musical scores for their particular instrument.