题干

下列水溶液中的各组离子因为发生氧化还原反应而不能大量共存的是             

A:Na+、Ba2+、Cl-、SO42-

B:Ca2+、HCO3-、C1-、K+

C:MnO4-、K+、I-、H+

D:H+、Cl-、Na+、CO32-

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C

同类题3

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    If English means endless new words, difficult grammar and sometimes strange pronunciation, you are wrong. Haven't you noticed that you have become smarter since you started to learn a language?

    According to a new study by a British university, learning a second language can lead to an increase in your brain power. Researchers found that learning other languages changes grey mater. This is the area of the brain which processes information. It is similar to the way that exercise builds muscles.

    The study also found the effect is greater when the younger people learn a second language. A team led by Dr. Andrea Mechelli, from University College London, took a group of Britons who only spoke English. They were compared with a group of bilinguals who had learnt a second language before the age of five, as well as a number of later learners.

    Scans showed that grey mater density(密度) in the brain was greater in bilinguals than in people without a second language.

    “Our findings suggest that the structure of the brain is changed by the experience of learning a second language,” said the scientists. It means that the change itself increases the ability to learn.

    Professor Dylan Vaughan Jones of the University of Wales, has researched the link between bilingualism and maths skills. “Having two languages gives you two windows on the world and makes the brain more flexible,” he said. “You are actually going beyond language and have a better understanding of different ideas.”

    The findings were matched in a study of native Italian speakers who had learned English as a second language between the ages of two and thirty-four. Reading, writing, and comprehension were all tested. The results showed that the younger they started to learn, the better. “Studying a language means you get an entrance to another world,” explained the scientists.

同类题5

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    About 30 years ago, I left Cuba for the United States with my son. After getting settled finally in Brunswick, New Jersey, I enrolled(注册) my son in kindergarten. Several weeks later, my son’s teacher asked me to meet him at his office.

    In the teacher’s office, and exchange of greetings was followed by his questions: “Is your son mentally retarded(弱智的)?Does he suffer from any kind of mental disability?”

    Was he talking about my wonderful Scola? NO, no, it can’t be. What a helpless, lonely moment! I told him that Scola was a quiet, sweet little boy, instead. I asked him why he was asking me all these questions.

    My son could not follow the teacher’s directions, he told me, and thus, Scola was disrupting the class, Didn’t he know my son did not speak English yet?

    He was angry; “Why hasn’t your son been taught to speak English? Don’t you speak English at home?”

    No, I didn’t speak English at home, I replied. I was sure my son would learn English in a couple of months, and I didn't want him to forget his native language. Well, wrong answer! What kind of person would not speak in English to her son at home and at all time? “Are you one of those people who come to this country to save dollars and send them back to their country, never wanting to be a part of this society?”

    Needless to say, I tried to tell him I was not one of “those people.” Then he told me the meeting was over, and I left.

    As I had expected, my son learned to speak English fluently before the school year was over. He went on to graduate from college and got a job, earning close to six figures. He travels widely and leads a well-adjusted, contented life. And he has benefited from being bilingual(双语的)。

    Speaking more than one language allows people to communicate with others; it teaches people about other cultures and other places—something very basic and obviously lacking in the “educator” I met in New Jersey.