基牙B6为第三类导线，应采用哪类卡环（）
A.单臂卡环
B.双臂卡环
C.间隙卡环
D.上返卡环
E.下返卡环
参考答案：E
The Whites _______many places of interest since they came to China. [ ]
A. have visited
B. will visit
C. visited
D. visit
区域客户主任日志需记录的内容是什么？
