题干

右图是实验室里一瓶标签破损的白色粉末状固体。小明同学取出少量该固体放入一洁净试管中,加水振荡后固体溶解,形成无色透明溶液,继续加入少量
盐酸,有无色无味的气体产生。该固体可能是下列物质中的()

A:Na2SO4

B:NaCl

C:NaHCO3

D:NaOH

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C

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    October 15th is the Global Hand washing Day. Activities are planned in more than 20 countries to get millions of people in the developing world to wash their hands with soap(肥皂). For example, donators(捐献者)will give 150,000 bars of soap to schools in Ethiopia.

    Experts say people around the world wash their hands every day, but very few use soap at so-called important moments. These include after using the toilet, after cleaning a baby and before touching food.

    Global Hand washing Day is the idea of the Public-Private Partnership for Hand washing with Soap. Partners include the United Nations Children's Fund, American government agencies, the World Bank and soap makers Unlever and Procter and Gamble. The organizers say all soaps are equally effective at removing disease-causing germ(细菌). They say the correct way to wash is to wet your hands with a small amount of water and cover them with soap. Rub it into all areas, including under the fingernails. Rub for at least twenty seconds. Then rinse well under running water. Finally, dry your hands with a clean cloth or wave them in the air.

    The Partnership for Hand washing says soap is important because it increases the time that people spend in washing hands. Soap also helps to break up the dirt that holds most of the germs. And it usually leaves a pleasant smell. The Partnership for Hand washing also says washing with soap before eating or after using the toilet could save more lives than any vaccine(疫苗)or medicine. Hand washing could also prevent the spread of other diseases. When people get germs on their hands, they can infect(传染)themselves by touching their eyes, noses or mouths. Then they can infect others.