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问题 选择题

下列说法正确的是(       )

A．相对原子质量和相对分子质量分别是原子、分子的质量

B．铁生锈是缓慢氧化，属于物理变化

C．构成物质粒子有分子、原子、离子等

D．由同种元素组成的物质叫单质

答案

答案：C

题目分析：A、原子质量是原子的实际质量，单位为g或Kg，而相对原子质量只是一个比值，故A说法错误；

B、铁生锈是缓慢氧化，有新的物质生成，属于化学变化，故B说法错误；

C、物质构成的微粒有分子、原子、离子，故C说法正确；

D、由同种元素组成的纯净物叫做单质，氧气、臭氧都是氧元素组成的，但二者混合后只含一种元素氧元素，属于混合物，故D说法错误；

故选C。

点评：本题难度不大，对于基本概念的理解同学们要重点掌握概念中的关键词语。

填空题

Good afternoon, everybody. I’m pleased to be here with you, graduates of 2007. I’m a (1) , and students often approach me with (2) . You see, we are living in a society of great changes. With the presence of (3) , the process of getting a job in today’s world has changed for (4) .
Well, how can you use new technologies to help you First, let’s look at how you (5) . The traditional method of hunting for a job in the past required first, doing research on jobs that were (6) , typically by looking in newspapers, periodicals and magazines, as well as TV ads, and (7) . Then you decided where and for what post you were going to apply, put your resume (8) in a stamped envelope, and waited anxiously for someone to (9) .
Well, today, maybe the job search and (10) are very much the same, but the tools used are much more advanced, and they (11) . In fact, technology has not so much changed the process as enhanced it. The benefit, both for (12) , is that this makes the search more open to people of (13) from all over the world. But as more people are involved, it becomes (14) for the applicant than it ever was before.
The (15) for the working world today is learning these new and (16) and combining them with the older methods people have been using for years. For example, (17) , you can research employment not just in your city, but also in your state, your country, and (18) . You can copy information from a web page and paste it into a Microsoft Word document that’s easy to (19) . In many ways, it’s easier now: Just type your job application, click, and (20) ; it gets there in an instant.
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单项选择题

10 BASE-T以太网，结点通过双绞线连接到一个集线器Hub上，其物理结构为______，逻辑结构为______。

A．总线型，总线型

B．星型，星型

C．星型，总线型

D．总线型，星型
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