固位和稳定效果最好的卡环是（）
A.单臂卡环
B.双臂卡环
C.三臂卡环
D.圈形卡环
E.间隙卡环
参考答案：C
Electricity plays _____ part in our life that it is unimaginable to live without it. [ ]
A. such important
B. so important
C. such important a
D. so important a
咳血方的臣药是（）
A.青黛、栀子
B.瓜蒌、海粉
C.当归、川芎
D.柴胡、大黄
E.桃仁、红花
