一般超声波美容仪的输出波形包括（）和脉冲波。
A.短波
B.连续波
C.断续波
D.长波
参考答案：B
When was ______ that the suggestion was put forward ______ the seven-day Labor Day Golden Week holiday be cancelled? [ ]
A. that; that
B. it; which
C. it; that
D. that; what
液氧中的乙炔等碳氢化合物含量过高时，应采取的措施？
