题干

在做下列物质在氧(或空气)中燃烧的实验时,要预先在集气瓶底放少量水,可以用细沙代替水的是(   )

A:硫

B:红磷

C:铁丝

D:以上全都可以

上一题 下一题 0.0难度 选择题 更新时间:2018-06-30 06:03:09

答案(点此获取答案解析)

C

同类题1

阅读理解

    Something's happening at the lowest point on our planet.

    The Dead Sea, a salt lake bordered by Jordan to the east and Israel and Palestine to the west, is shrinking(缩小) at an alarming rate-----about 3.3 feet per year, according to the environmentalist group EcoPeace Middle East. And human actions are largely to blame.

    “It's not just like one country is punishing the Dead Sea; it's more like the whole area,” said photographer Mortize Kustner, who visited the area in February to work on his series “The Dying Dead Sea”.

    The Dead Sea needs water from the other natural sources surrounding it, such as the Jordan River basin. But around the 1960s, some of the water sources it relied on were diverted(使改道).Israel, for instance, built a pipeline during that time so it could supply water throughout the country.

    Mineral extraction(开采) industries are another main reason the water levels are falling, experts say. The Dead Sea's minerals have been used as medicine and can often be found in cosmetics(化妆品) and other consumer products.

    And then, of course, there's the Middle East's hot, dry climate, which makes it difficult for the lake to replenish itself.

    Last year, Israel and Jordan signed a $900 million deal in an effort to keep the Dead Sea's water levels stable(稳定). It includes building a canal from the Red Sea to the Dead Sea which would be able to not only supply water to Israel and Jordan but also to pump water into the Dead Sea.

    But for now, Kustner shows us that the Dead Sea remains very much a place of interest, with people from all over the world going there to swim in its salty waters.

    The Dead Sea, known as the Salt Sea in the language of Hebrew, is one of the saltiest bodies of water in the world. And because of what has been happening over the years, the salt is only getting saltier.

同类题2

阅读下列短文,根据短文内容,从短文后各题所给的A、B、C、 D四个选项中,选择最佳选项。

How to Be a Better Student

    Maybe you are a common student. You probably think you will never be a top student. This is not necessary so, however. Anyone can become a better student if he or she wants to. Here's how:

Plan your time carefully. When you plan your week, you should make a list of things that you have to do. After making this list, you should make a schedule of your time. First set your time for eating, sleeping, dressing, etc. Then decide a good, regular time for studying. Don't forget to set aside enough time for entertainment. A weekly schedule may not solve all your problems, but it will force you to realize what is happening to your time.

    Find a good place to study. Look around the house for a good study area. Keep this space, which may be a desk or simply a corner of your room, free of everything but study materials. No games, radios, or television! When you sit down to study, concentrate on the subject.

    Make good use of your time in class. Take advantage of class time to listen to everything the teachers say. Really listening in class means less work later. Taking notes will help you remember what the teacher says.

    Study regularly. When you get home from school, go over your notes, review the important points that your teacher is going to discuss the next day, read that material. This will help you understand the next class. If you do these things regularly, the material will become more meaningful, and you will remember it longer.

    Develop a good attitude about tests. The purpose of a test is to show what you have learned about a subject. They help you remember your new knowledge. The world won't end if you don't pass a test, so don't be over worried.

    There are other methods that might help you with your studying. You will probably discover them after you have tried these.