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类质同像代替的条件是什么？

答案

参考答案：

①相互取代的原子或离子，其半径应相近

②在类质同像的代替中，必须保持总价键的平衡

③惰性气体型离子在化合物中一般以离子键结合，而铜型离子在化合物中以共价键结合为主

④温度增高有利于类质同像的产生，而温度降低则将限制类质同像的范围并促使类质同像混晶发生分解

⑤一般来说，压力的增大将限制类质同像代替的范围并促使其离溶

单项选择题

女性，40岁，近2年来月经量增多，无腹痛，妇科普查时发现子宫2个月妊娠大小，不规则。拟诊为子宫肌瘤。

当子宫肌瘤发生变性时最少见的是哪一种

A．玻璃样变

B．囊性变

C．水样变性

D．红色变性

E．肉瘤样变
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单项选择题

A good modern newspaper is an extraordinary piece of reading. It is remarkable first for what it contains the range of news from local crime to international politics, from sports to business to fashion to science, and the range of comment and special features (特定) as well, from editorial page to feature articles and interviews to criticism of books, art, theatre and music. A newspaper is even more remarkable for the way one reads it never completely, never straight through, but always by jumping from here to there, in and out glancing at one piece, reading another article all the way through, reading just a few paragraphs of the next.
A good modern newspaper offers a variety to attract many different readers, but far more than any one reader is interested in. What brings this variety together in one place is its topicality (时事性), its immediate relation to what is happening in your world and your locality now. But immediacy and the speed of production that goes with it mean also that much of what appears in a newspaper has no more than transient (短暂的) value.
For all these reasons, no two people really read the same paper: what each person does is to put together out of the pages of that day’s paper, his own selection and sequence, his own news paper. For all these reasons, reading newspapers efficiently, which means getting what you want from them without missing things you need but without wasting time, demands skill and self-awareness as you modify and apply the techniques of reading.

A good newspaper offers a variety to readers because ______.

A. it tries to serve different readers
B. it has to cover things that happen in a certain locality
C. readers are difficult to please
D. readers like to read different newspapers
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