若直线x=1的倾斜角为α，则α等于（ ）
A．0°
B．45°
C．90°
D．不存在
直线x=1与x轴垂直，故直线的倾斜角是90°，
故选 C．
香豆素
Wei Fang is as as Li Ling. [ ]
A. carefully
B. more carefully
C. careful
