If `(alpha, beta)` is the foot of perpendicular from `(x_1, y_1)` to line `lx+my+n=0`, then (A) `(x_1 - alpha)/l = (y_1 - beta)/m` (B) `(x-1 - alpha)/l) = (lx_1 + my_1 + n)/(l^2+m^2)` (C) `(y_1 - beta)/m = (lx_1 + my_1 +n)/(l^2 +m^2)` (D) `(x-alpha)/l = (lalpha+mbeta+n)/(l^2+m^2)`