A.高頻段B.中頻段C.低頻段D.中高頻段
A.順時針轉(zhuǎn)過π弧度B.順時針轉(zhuǎn)過2π弧度C.逆時針轉(zhuǎn)過π弧度D.逆時針轉(zhuǎn)過2π弧度
A.0B.1C.2D.3