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问题 填空题

(1)短周期元素X、Y、Z位置关系如图所示

①X元素形成的单质的化学式是__________。若X核内中子数与质子数相等，X单质的摩尔质量是__________。

②Z单质的晶体类型属于_________。Z与Na 形成的化合物的电子式为____________。

(2)已知下列元素的原子半径：

根据以上数据判断磷原子的半径可能的范围在______________________。

答案

(1)①He；4g/mol；②分子晶体；

(2)1.02×10-10～1.17×10-10m

完形填空

根据下面短文内容，在短文的空格处填上一个恰当的词，使短文完整、通顺。

“Cool” is a word with many meanings. Its old meaning is   小题1:  to express a temperature that is a little bit cold. As the world has changed, the word has had many different   小题2: . “Cool” can be used to express feelings of interest in almost anything.

 小题3:  you see a famous car in the street, maybe you will say, “It’s cool.” You may think, “He’s so cool,” when you see your favorite footballer. We all maximize(最大化) the meaning of “cool”. You can use it   小题4:  of many words such as “new” or “surprising”. Here’s an interesting story we can use to show the way the word is used. A teacher asked her students to write about the waterfall(瀑布) they had visited. On one student’s paper was just the one sentence, “It’s so cool.” Maybe he thought it was the 小题5:  way to show what he saw and felt.

But the story also shows a scarcity(缺乏) of words.  小题6:  “cool”, some people have no words to show the same meaning. Can you think of many  小题7:  words that make your life as colorful as the word “cool”? I can. And I think they are   小题8:  very cool.
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单项选择题

事务是数据库技术中一个非常重要的概念。下列关于事务的说法，错误的是______。

A) 当某事务未执行完成时，数据库暂时处于不一致状态，这时其他事务不会因这种不一致状态而出现数据错误
B) 事务并发执行可以提高系统性能，但可能会导致数据出现问题。为了保证数据库数据的一致性，对事务的调度一般尽可能采用串行调度策略
C) 利用日志文件进行数据库事务故障恢复和系统故障恢复是实现事务持久性的重要手段
D) 存储管理器以事务方式访问数据库中的数据，确保数据库状态的一致性
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