To form an ellipse, what is the relationship between the base of the cone and the angle of the plane that intersects the cone?
a
The plane is parallel to the base of the cone.
b
The plane may be perpendicular to the base of the cone.
c
The plane is at an angle that is neither parallel nor perpendicular to the base of the cone.
d
The plane must be at a 45° angle to the base of the cone.