问题 选择题

今年世界各国频发地震。为防止震后疾病传染须对饮用水源进行处理,采取的措施有:

①煮沸 ②消毒 ③过滤 ④自然沉降,合理处理的顺序是

A.③①②④

B.②④③①

C.④③①②

D.④③②①

答案

答案:D

考点:

专题:实验设计题.

分析:净化水常用的方法有沉降、吸附、过滤、蒸馏、消毒杀菌.分析水处理措施的作用,对处理措施进行排序.

解答:解:①煮沸,通过加热煮沸,杀死水中病菌以便饮用;

②消毒,利用消毒杀菌剂杀死水中病菌;

③过滤,除去水中不溶性固体物质;

④自然沉降,通过静置,把水中不溶性固体与水初步分离;

因此处理水的合理顺序为:④③②①;

故选D

点评:净化水常用的方法有沉降、吸附、过滤、蒸馏、消毒杀菌,在这些方法中净化程度最高的为蒸馏.

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Smallpox was the first widespread disease to be eliminated by human intervention. A highly contagious viral disease, it was endemic in Europe, causing the death of millions of people until the development of vaccination by Edward Jenner around 1800. In many non- European nations, it remained a dreaded, often fatal illness until very recently.
In May 1966, the World Health Organization (WHO), an agency of the United Nations, was authorized to initiate a global campaign to eradicate smallpox. The goal was to eliminate the disease in one decade. At the time, the disease posed a serious threat to people in thirty nations. More than 700 physicians, nurses, scientists, and other personnel from WHO joined about 200,000 health workers in the infected nations to battle the disease. Because similar projects for malaria and yellow fever had failed, few believed that smallpox could actually be eradicated, but eleven years after the initial organization of the campaign, no cases were reported in the field.
The strategy was not only to provide mass vaccinations but also to isolate patients with active smallpox in order to contain the spread of the disease and to break the chain of human transmission. Rewards for reporting smallpox assisted in motivating the public to aid health workers. One by one, each smallpox victim was sought out, removed from contact with others and treated. At the same time, the entire village where the victim had lived was vaccinated.
By April 1978, WHO officials announced that they had isolated the last known case of the disease, but health workers continued to search for new cases for two additional years to be completely sure. In May 1980, a formal statement was made to the global community. Today smallpox is no longer a threat to humanity. Routine vaccinations have been stopped worldwide.

The word "isolated" underlined in Paragraph 4 most probably means ______ .

A.restored

B.separated

C.attended

D.located