The set of points on the axis of the parabola `y^2=4x+8` from which the three normals to the parabola are all real and different is (a) `{(k ,0)"|"klt=-2}` (b) `{(k ,0)"|"kgt=-2}` (c) `{(0, k)"|"k gt=-2}` (d) none of these