Two straight lines are perpendicular to each other. One of them touches the parabola `y^2=4a(x+a)` and the other touches `y^2=4b(x+b)` . Their point of intersection lies on the line. `x-a+b=0` (b) `x+a-b=0` `x+a+b=0` (d) `x-a-b=0`