The section plane intersects with the axis of the cone A. Circle B. Intersect two lines C. Ellipse

The section plane intersects with the axis of the cone A. Circle B. Intersect two lines C. Ellipse

Choose a and C
The section plane intersects with the axis of the cone. The shape of the section line is circle (the section plane is perpendicular to the axis) or ellipse (the section plane is not perpendicular to the axis)