Which of the following statements about dengue virus is not true?
A. It is the most important mosquito-borne viral disease affecting humans
B. It is distributed worldwide in tropical regions
C. It can cause a severe hemorrhagic fever
D. There is a single antigenic type
E. One form of disease is characterized by increased vascular permeability
The clinical picture of arbovirus infection fits one of three categories: encephalitis, hemorrhagic fever, or fever with myalgia. One of the characteristics of arbovirus is that they
Are transmitted by arthropod vectors
B. Are usually resistant to ether
C. Usually cause symptomatic infection in humans
D. Are closely related to parvoviruses
说明消失模铸铁件表面皱皮缺陷概念，产生原因及影响因素。
社会主义的根本任务是____。
A. 发展经济
B. 解放和发展社会生产力
C. 实现工业化
D. 实现社会和谐
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