按滤波方式分类，变频器分为（）、（）。
参考答案：电压型变频器；电流型变频器
They are good friends and they many happiness and sorrows together.
A．had lived through
B．live through
C．lived through
D．have lived through
2000年境内应纳所得税为( )万元。
A．30
B．31
C．32
D．33
