[题目]直线 dfrac (x+1)(-1)=dfrac (y-2)(1)=dfrac (z-1)(0) 与平面 4x+y+z=1 的-|||-夹角为() ()-|||-A. dfrac (pi )(6)-|||-B. dfrac (pi )(3)-|||-C. cos dfrac (2)(3)-|||-D. dfrac (pi )(4)