下列哪些原因使能见度受到限制，不属于能见度不良？（）。
A.夜间漆黑
B.雾
C.下雪
D.暴风雨
参考答案：A
A．mgtgθ
B．mgsinθ
C．μmg
D．μmg
The late Pope had cured himself of Parkinson’s disease, thus moving a step closer to sainthood.
mgtgθ
mgsinθ