You can
put this solution on YOUR website!Circle: pass the plane thru the cone parallel to the base
Ellipse: pass the plane thru the cone but not parallel to the base
Parabola: pass the plane thru the cone parallel to the vertical axis of the cone
Hyperbola: Put one cone on top of the other---tip to tip.
pass the plane thru the double cone parallel to the vertical axis of the cone
Cheers,
Stan H.