Which intersection forms a circle?

A plane intersects only one nappe of a double-napped cone, and the plane is perpendicular to the generating line of the cone.

A plane intersects only one nappe of a double-napped cone, and the plane is parallel to the generating line of the cone.

A plane intersects only one nappe of a double-napped cone, and the plane is perpendicular to the axis of the cone.

A plane intersects both nappes of a double-napped cone, and the plane does not intersect the vertex.