In the first paragraph, homeland security is mentioned to______. A．serve as the topic of this text B．discuss the importance of budget C．make comparison with flood defence D．introduce the discussion of natural threats
A. A．serve B.discuss C.make D.introduce
【参考答案】
D 根据题干定位到第一段。文章第一句提到homelandsecurity“国土安全”一词，但是从第二段开始就没有......