________ we stood at the top of the building, we were able to enjoy the town below clearly.[ ]

A. As  

B. Although

C. Unless  

D. Until

口角线是（）

A．微张口时上唇下缘的位置线

B．微张口时下唇上缘的位置线

C．微笑时上唇下缘的位置线

D．微笑时下唇上缘的位置线

E．垂直于平面的直线