部队证件中有水印的证件是（）。
A.士兵证
B.军官证
C.警官证
D.警察证
参考答案：B, C
圆x2+y2+4x-2y-4=0的圆心的坐标是______，半径长等于______．
It’s essential for citizens to know that the haze(雾霾.can do harm ________ people’s health.
A．with
B．for
C．on
D．to
