问题
填空题
源在外双壁透照环焊缝时，焦距越大，则有效透照长度（）。
答案
参考答案：越小
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源在外双壁透照环焊缝时，焦距越大，则有效透照长度（）。
参考答案：越小
完形填空。阅读下面短文，选择最佳作案。（每小题1分，共10分） The Great Wall of China has a history of over two thousand years. It runs from the east to the west in North China . It is about 6,300 kilometers 46 . It is often 47 “The Ten-thousand- Li Great Wall”. It is one of the “Seven Wonders” of the ancient world. The Great Wall is 48 for ten men to walk side by side. Horses can also run along it, too. The Great Wall 49 stones and bricks(砖). There are huge stones on 50 side and on the highest part. But now some sections of it are worn out. There are tall watchtowers along the Great Wall. Once upon a time, the soldiers kept 51 the enemies(敌人) in the watchtowers day and night. They made 52 on the towers to 53 each other when the enemies came. Nowadays we don’t use the Great Wall to keep away the enemies any more. It is a famous place of 54 to all the people in the world. Every year 55 people come to visit it from all over the world.
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