题目内容

当驱动电动机转动时,带动联轴器与()同步旋转。

A. 蜗轮
B. 蜗杆
C. 曳引轮
D. 导向轮

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离子交换柱上的操作一般过程是:交换、洗涤、洗脱和再生。

A. 正确
B. 错误

消弧线圈、干式电抗器、干式变压器绕组绝缘电阻标准是()。

A. 绝缘电阻无显著下降
B. 吸收比大于等于1.3
C. 极化指数大于等于1.5
D. 绝缘电阻大于等于10000M&Omega

工件坐标系是机床进行加工时使用的坐标系,它应该与编程坐标系一致

A. 正确
B. 错误

Exports are either raw materials or manufactured goods. Raw materials are products of the land, such as cotton, timber or rubber. Some raw materials, such as iron ore, come from mines. These raw materials are often exported by the countries that produce them to other countries where they are made into manufactured goods. Some countries produce food for export, for example, meat, sugar, or cereals such as wheat and maize. These countries are agricultural countries. An agricultural country needs fertile land and a good climate. A cold, dry climate is not suitable for agriculture. A country which produces manufactured goods is known as an industrialized country. An industrialized country cannot always produce enough food for its own needs. In this case, it does not export foodstuffs. Instead it has to import them. It relies on exports of manufactured products and pays for imports with the money it earns from the exported goods. An industrialized country usually has to import foodstuffs because,().

A. it cannot always produce enough food for its own needs
B. it doesn't has fertile land and a good climate
C. it relies on exports of manufactured product

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