单项选择题

以下 ( )矿物的断口是贝壳状断口。 A. 自然金 B. 石英 C. 高岭石 D. 纤维石膏

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法国最具有代表性的帝国风格建筑是：（）

答案：正确答案：雄狮凯旋门

多项选择题

The operating status of the current transformer is characterized by ()
A、The primary winding is connected in series in the primary circuit
B、 Under normal circumstances, the ct is close to short-circuit operation
C、 The primary current has nothing to do with the change of the secondary load
D、Open circuit of secondary winding is not allowed during operation