患者男,缺失,余留牙未见异常,可摘局部义齿修复,做基牙,采用铸造卡环
应该采用何种卡环()
A.双臂卡环
B.单臂卡环
C.对半卡环
D.下返卡环
E.RPI卡环
参考答案:E
Tom's never been abroad before, _______ he? [ ]
A. isn't
B. has
C. does
D. is
简要回答从犯的概念及其刑事责任。