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炼铁的主要原料是______、焦炭、石灰石，主要设备是______．与生铁相比，钢的含碳量比生铁______（高、低）．

答案

工业炼铁在高炉中进行，主要原料有：铁矿石、焦炭和石灰石；焦炭在过量空气中生成二氧化碳，同时放出大量热，二氧化碳又在焦炭的作用下生成一氧化碳，一氧化碳把铁从铁矿石中还原出来，从而制得铁．

生铁是含碳量为2%～4.3%的铁合金，钢是含碳量为0.03%～2%的铁合金，与生铁相比，钢的含碳量比生铁低．

故答案为：铁矿石；高炉；低．

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在平面直角坐标系xoy中，直线ax+2y+3a=0和直线3x（a-1）y=a-7平行的充要条件是______．
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Most "unassertive" people are not confident and take no for an answer much too easily. There is a growing awareness in our society that this tendency (1) the rights of large numbers of people. For example, in recent years there has been an upsurge in (2) and pressure groups. This is a (3) as there will always be a need for such organizations to (4) individuals and minorities in a competitive society. The danger is that we (5) for our rights and lose the art of asserting ourselves. It is better for (6) with other people if you can learn (7) for yourself.
Now, we have to learn to ignore some of the (8) that may be ringing in our unconscious minds, such as: "If you ask once more, I’ll flatten you", and " (9) ".
The main technique that we use in (10) to practice the art of persistence is called Broken Record. (11) we hear one sentence over and over again until we reach screaming pitch and (12) .
Broken Record is the skill of being able to repeat over and over again, (13) , what it is you want or need, until the other person gives in or (14) .
Now, this technique is extremely useful for dealing with situations where your rights are clearly (15) , or coping with situations where you are likely to be diverted by clever, (16) .
The beauty of using Broken Record is that you (17) because you know exactly what you are going to say, however (18) the other person tries to be.
As with most assertive techniques, it must be used appropriately. It is (19) and is not designed to foster deep, interesting conversations and friendships with people! It is primarily of use in situations where (20) .
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