第7题: [填空题]The filter of Ceramic Water Purifier is also painted with colloidal silver because it is used in water purification systems in many aircraft. 参考答案:N 答案解析:[分析] 参见第四段。尽管此段提到colloidal silver被应用于许多飞机的净水系统这是一个事实,但过滤器外再涂一层colloidal silver的原因是 Colloidal silver