变频器的干扰处理的一般方式有（）。
A、加隔离变压器
B、使用滤波器
C、使用输出电抗器
D、接地
参考答案：A, B, C, D
(2013·辽宁师范大学附中模拟)Fortunately it happened at night. If the hurricane ________ during the daytime, there ________ more deaths.
A．had happened; would have been
B．happened; would be
C．had happened; would be
D．happened; would have been
超高层建筑通常采用钢筋混凝土框架结构。
