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  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
【C2】
选项
答案H
解析 此处应填形容词。因为空格后的it指代的是influenza，下文中主要讲的就是三种病毒引起的流感的传染性和严重程度，前面的when and where the…will occur是说influenza的传染性，那么空格处就应是讲其“严重”性了，故选H)severe。
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