Which intersection forms a circle? A. A plane intersects only one nappe of a double-napped cone such that the plane is parallel to the generating line.

B. A plane intersects only one nappe of a double-napped cone. The plane is neither perpendicular to the axis nor parallel to the generating line.

C. A plane intersects only one nappe of a double-napped cone such that the plane is perpendicular to its axis.

D. A plane intersects both nappes of a double-napped cone.