题干

山茶油是一种绿色保健食品,其主要成分是柠檬醛。现从山茶油中提取7.6 g柠檬醛,使其在氧气中完全燃烧,生成22 g二氧化碳和7.2 g水,则柠檬醛中

A:只含有碳、氢元素

B:一定含有碳、氢、氧元素

C:含有的元素无法确定

D:一定含有碳、氢元素,可能含有氧元素

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答案(点此获取答案解析)

B

同类题3

根据短文内容,选择正确答案。

                                                                                               C

    As you touch people and objects throughout the day, there are germs(细菌) on your hands. In turn, you can make yourself ill with these germs by touching your eyes, nose or mouth. Although it's impossible to keep your hands germ-free, washing your hands is good for you. It limits the chance of getting sick and is one of the best ways to avoid(避免) getting sick and spreading illness. Staying healthy can make you feel happier.

    Hand washing requires only soap and water, but do you really know when and how to wash your hands? The following information may be useful for you.

    When to wash your hands

    Always wash your hands before:

    ▲Preparing food

    ▲Eating

    ▲Giving medicine

    ▲Touching a sick or injured person Always wash your hands after:

    ▲Preparing food

    ▲Using the toilet

    ▲Touching an animal or animal toys or waste

    ▲Touching a sick or injured person

    Of course, it's also important to wash your hands whenever they look dirty.

    How to wash your hands

    It's generally best to wash your hands with soap and water. Follow these simple steps:

    ▲Wet your hands with running water.

    ▲Use soap.

    ▲Wash your hands for at least 20 seconds. Remember to wash the hands carefully, including the backs of your hands, wrists, fingers and fingernails.

    ▲Dry your hands with a clean towel.