在交变电场作用下，绝缘中消耗的能量称为介质损耗。
参考答案：对
There are ________ students waiting in the hall ________?[ ]
A. hundreds of; aren't they
B. four hundred; aren't they
C. four hundreds; aren't there
D. hundreds of; aren't there
已知某商品流通企业第20个周期的平滑系数A20＝918.5，B20=105，用二次平滑指数平滑法预测第25个周期的销售量为( )台。
A．1023.5
B．1443.5
C．4697.5
D．5117.5
