导线切割前对切割部位两侧采取绑扎措施，防止导线抛股，导线断面应与轴线（），引下线及跳

设等差数列前n项和为S_n，已知a₃=12，S₁₂＞0，S₁₃＜0，

（1）求公差d的取值范围；

（2）指出S₁，S₂，S₃，…，S₁₂中哪一个值最大，并说明理由。

成品油生产商的利润很大程度上受国际市场原油价格的影响，因为大部分原油是按国际市场价购进的。近年来，随着国际原油市场价格的不断提高，成品油生产商的运营成本大幅度增加。但某国成品油生产商的利润并没有减少，反而增加了。 以下哪项如果为真。最有助于解释上述看似矛盾的现象

A．原油成本只占成品油生产商运营成本的一半

B．该国成品油价格根据市场供需确定。随着国际原油市场价格的上涨，该国政府为成品油生产商提供相应的补助

C．在国际原油市场价格不断上涨期间，该国成品油生产商降低了个别高薪雇员的工资

D．该国成品油生产商的原油有一部分来自国内，这部分受国际市场价格波动影响较小

简述男装向现代形态转变的过程，并分析其成因。

You can tell the age of a tree by counting its ring. But these records of a tree’s life really say a lot more. Scientists are using tree ring to learn what’s been happening on the sun’s surface for the last ten thousand years. Each ring represents a year of growth. As the tree grows, it adds a layer to its trunk, taking up chemical elements from the air. By looking at elements in the rings from a certain years, scientists can tell what elements were in the air that year. Dr. Stevenson is analyzing one element, carbon-14, in ring from both living and dead tree. Some ring go back almost ten thousand year to the end of the Ice Age. When Stevenson followed the carbon-14 levels changed with the intensity of solar burning. You see, the sun has cycles. Sometimes it bums fiercely, and at other times it is relatively calm. During the sun’s violent periods, it throw off charged particles in fast moving streams called "solar winds". The particularly interfere with the formation of carbon-14 on earth. When there is more solar wind activity, less carbon-14 is produced. Ten thousand years of tree ring show that the carbon-14 level rises and falls about every 420 years. The scientists concluded that solar wind activity must follow the same cycle.

When the sun burn fiercely, () carbon-14 is produced.

A. less

B. more

C. no

D. much

激光打印机具有噪声大、印字质量好等特点。