A cone is cut through a plane parallel to its base and then the cone that is formed on one side of that plane is removed. The new part that is left over on the other side of the plane is called
A frustum of a cone
Explanation for the correct answer:
When a cone is divided into two parts by a plane through any point on its axis parallel to its base, then the upper and lower parts obtained are cone and a frustum respectively.
The figure given below depicts how the shapes are formed when a cone is cut into two parts on its axis parallel to its base.
Hence, option A is correct.