Which of the following line, is a normal to the parabola `y^2=16x?`

The locus of the midpoints of the portion of the normal to the parabola y^(2)=16x intercepted between the curve and the axis is another parabola whose latus rectum is ___________ .

The locus of the midpoints of the portion of the normal to the parabola y^(2)=16x intercepted between the curve and the axis is another parabola whose latus rectum is ___________ .

The locus of the midpoints of the portion of the normal to the parabola y^(2)=16x intercepted between the curve and the axis is another parabola whose latus rectum is ___________ .

The line y=2x+k is a normal to the parabola y^(2)=4x then k=

The line y=2 x+k is a normal to the parabola y^(2)=4 x, then k=