第4题: [单项选择]People should be able to come to a decision about ions in the air if they _______. A. note their own reactions B. move to a healthier, area C. observe domestic animals D. watch how wealthy people behave 参考答案:A 答案解析:[解析] 事实细节题。根据文章倒数第二句,人们可以通过观察负离子富含或缺乏对自己的影响作决定,即观察自己的反应,所以选[A]。第三题中提到人们观察动物是为了预报灾难,不用来决定负离子数量是否合适,排除