交流滤波器的设备状态有哪几种。（）
A.检修
B.冷备用
C.热备用
D.运行
参考答案：A, B, C, D
I looked up and noticed a snake ________its way up the tree to catch its breakfast.[ ]
A. to wind
B. wind
C. winding
D. wound
模像直观
