为减少修复体对牙周组织的刺激，冠的边缘最好位于（）。

A.尽量放在牙龈缘的冠方

B.尽量放在牙龈缘以下

C.放在龈缘以下近龈沟底

D.放在龈缘以下距沟底1mm处

E.放在牙龈缘平齐的位置

(2014·皖南八校联考)________ Yao Ming has retired from the NBA，the pleasure we have got by watching him play basketball at home and abroad will last long.

A．Although　

B．If

C．Since　

D．Once