问题
多项选择题
有关对称三相电源的星形联结方式，以下说法正确的是（）。
A、可做三相三线制联结
B、在低压系统中，做三相四线制
C、线电压的相位超前相应的相电压30°
D、线电压的有效值是相电压的3倍
E、不可做三相三线制联结
答案
参考答案：A, B, C
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有关对称三相电源的星形联结方式，以下说法正确的是（）。
A、可做三相三线制联结
B、在低压系统中，做三相四线制
C、线电压的相位超前相应的相电压30°
D、线电压的有效值是相电压的3倍
E、不可做三相三线制联结
参考答案：A, B, C
A winter storm (暴风雪) usually can last for some time with high winds, cold rain, heavy snowfall (降雪) and low temperature. Winter storms can make driving and walking dangerous. Before a winter storm: ◆Have a good plan. ◆Buy some food, water and warm clothes for your family. ◆Always listen to the weather report for your area. During a winter storm: ◆Stay at home and wear warm clothes. ◆Eat more food and drink more water. ◆If you must drive, carry a cell phone . After a winter storm: ◆Don’t drive until the weather gets better. ◆Check on your neighbors to make sure that they’re OK. 请根据材料内容完成下面表格，每空词数不限。
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