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對于晶體的x射線衍射，主極大的位置由下列那個公式確定[ ]
We ail know that it is possible for ordinary people to make their homes on the equator (赤道) ,although often they may feel uncomfortably hot there. Millions do it. But as for the North Pole (北極)—we know that it is not only a dangerously cold place, but that people like you and I would find it quite impossible to live there. At the present time only the scientists and explorers can do so, and they use special equipment. (76)Men have been travelling across and around the equator on wheels, on their feet or in ships for thousands of years; but only a few men, with great difficulty and in very recent time. have ever crossed the ice to the North Pole. So it may surprise you to learn that, when traveling by air, it is really safer to fly over the North Pole than over the equator. Of course, it is not true about landings in the polar region, but the weather, if we are flying at a height of 5,000 meters above the Pole is a delight. At 4,000 meters and move above the earth you can always be sure that you will not see a cloud in the sky as far as your eyes can reach. In the tropics (熱帶), on the other hand, you are not certain to keep clear of bad weather even at such heights as 18,000 or 20,000 meters.Nowadays most people decide quite【61】what kind of work they would do. When I was at school, we had to choose【62】when we were fifteen. I chose scientific subjects. "【63】, scientists will earn a lot of money," my parents said.【64】I tried to learn physics and chemistry, but in the【65】I decided that I【66】a scientist. It was a long time【67】I told my parents that I wasn't happy at school. " I didn't think you were," said my mother. "【68】," said my father. "Well, the best thing to do now is to look for a job. "下列情況中應澆灑黏層瀝青的是()。。
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