Which of the following best states the main idea of the passage?

• A、It is easier to study medicine than music.
  
  

• B、Painters and composers use totally different methods to reach the public.
  
  

• C、All musicians must know how to time their own instruments.
  
  

• D、Musicians must acquire technique and understanding to perform well.
  
  

If a person's family has had an ulcer, he is three times more likely to get ulcer than people

without a family history of ulcers.

• A、True
  
  

• B、False
  
  

• C、Not Given
  
  

下面的短文有10处空白，每处空白后的括号内有一个词，请根据短文内容将其正确的形式填入文中，以恢复文章原貌。

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) .