2. 外语
  3. Although we already know a great deal about influenza, it is difficult for epidemiologists(流行病学家), who study infectious disease,

Although we already know a great deal about influenza, it is difficult for epidemiologists(流行病学家), who study infectious disease,

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问题     Although we already know a great deal about influenza, it is difficult for epidemiologists(流行病学家), who study infectious disease, to【C1】______when and where the next flu epidemic will occur, and how【C2】______it will be. There are three kinds of influenza virus, known as A, B and C. Influenza C virus is relatively stable and causes mild【C3】______that do not spread far through the population. The A and B types are【C4】______, and are responsible for the epidemics that cause frequent concern. Following any virus attack, the human body builds up antibodies which confer(给予)immunity to that strain of virus, but a virus with the capacity to change its character is able to bypass this【C5】______. Variability is less developed in the influenza B virus, which affects only human beings. An influenza B virus may cause a widespread epidemic but will have little effect if【C6】______into the same community soon afterwards, since nearly everyone will have built up antibodies and will be immune. The influenza A virus, which【C7】______affects animals, is extremely unstable and is responsible for some of the worst outbreaks of the disease, such as the unparalleled pandemic, or world epidemic. Accurate prediction is difficult because of the complication of the【C8】______. A particular virus may be related to one to which some of the population have【C9】______involved immunity. The extent to which it will spread will depend on factors such as its own strength, or virulence, the ease with which it can be【C10】______and the strength of the opposition it encounters. Scientists, however, have a reliable general picture of the world situation, according to which we may take some precautions.
A)partially I)epidemics
B)guess J)also
C)factors K)attacks
D)equally L)introduced
E)generally M)unstable
F)protection N)infections
G)transmitted 0)predict
H)severe
【C6】
选项
答案L
解析 此处应填动词。分析句子结构可知if后省略了it is，it指代influenza B virus。再根据主语与所填词的关系，如果表主动用现在分词，如果表被动则用过去分词。可选项有G)transmitted和L)introduced，确定它们是主语的被动动作。introduce into意为“传入，引入”，符合文意。transmit后面一般不接into，而接to表示传染的对象，故排除G)transmitted，选L)introduced。
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