T is a point on the tangent to a parabola y² = 4ax at its point P. TL and TN are the perpendiculars on the focal radius SP and the directrix of the parabola respectively. Then:

a) SL = 2 (TN)
b)3 (SL) = 2 (TN)
c) SL = TN
d) 2 (SL) = 3 (TN)