问题 单项选择题

可溶于碳酸氢钠溶液的是()。

A.喜树碱

B.石蒜碱

C.氧化苦参碱

D.麻黄碱

E.槟榔次碱

答案

参考答案:E

解析:本题考查要点是"生物碱的理化性质"。①喜树碱不溶于一般有机溶剂,而溶于酸性三氯甲烷等。②石蒜碱难溶于有机溶剂,而溶于水。③氧化苦参碱为含N-氧化结构的生物碱,这类生物碱具有配位键结构,可溶于水。④麻黄碱为小分子生物碱,少数分子较小而碱性较强的生物碱,即可溶于水,也可溶于三氯甲烷。⑤槟榔次碱为具有羟基的生物碱,这类见可溶于碳酸氢钠溶液。

阅读理解

第三部分阅读理解(共20小题;每小题2分,满分40分)

English is fast becoming the language of science around the world, but what is its future among everyday speakers? One expert points out that the percentage(比率) of native English speakers is declining(降低) globally while the languages of other rapidly growing regions are being spoken by increasing numbers of people. But English will continue to remain widespread and important.

However, British language scholar David Graddol says English will probably drop in dominance(主导) by the middle of this century to rank, after Chinese, about equally with Arabic, Hindi, and Urdu. “The number of people speaking English as a first language continues to rise, but it isn’t rising nearly as fast as the numbers of many other languages around the world, simply because the main population group has been largely in the less developed countries where languages other than English have been spoken,” he says.

In a recent article in the journal Science, Mr. Graddol noted that three languages that are not near the top of the list of the most widely spoken now might be there soon. These are Bengali, Tamil, and Malay, spoken in south and Southeast Asia.

David Crystal, the author of the Cambridge Encyclopedia of the English Language, says about 1.5 billion of the world’s six billion people speak it as a second tongue compared to the 400 million native speakers. But another expert on the English language says Mr. Graddol underestimates (低估) the future of its dominance. “Nobody quite knows what’s going to happen because no language has been in this position before. But all the evidence (证据) suggests that the English language snowball is rolling down a hill and is getting faster,” he said.

56. In David Graddol’s opinion, English will _______.

A. remain widespread and important

B. be more important than any other language

C. lose its dominant position

D. die away in the near future

57. The underlined sentence in the last paragraph implies that ______.

A. snowballs will roll down faster than language balls

B. the English language snowball is rolling down faster than any time in the past

C. English language will soon drop in dominance

D. more and more language users will choose English

58. How many experts does the passage mention who express their ideas about the future of English?

A. 2.          B. 3.         C. 4.           D. 5.

59. What should be the best title for the passage?

A. English Remaining the Dominant Position

B. The Future of English? Who Knows?

C. Opinions from Different Experts

D. The English Language Snowball Rolling Down

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