The old couple married for 40 years and never once____ with each other.

A．they had quarreled.

B．they have quarreled

C．have they quarreled

D．had they quarreled.

缺失，患者要求做可摘局部义齿修复。设计为上放置间隙卡环

若原天然牙扭转15°，缺失后间隙稍小，为恢复美观最佳的排牙方法应是（）

A.颈部排向唇侧，切缘排向腭侧

B.磨窄人工牙近远中后再排列

C.按照天然牙的扭转角度和方向排列

D.小，可排成侧切牙

E.把切缘排向唇侧，颈部排向腭侧