A cone is cut by a plane parallel to its base and the cone on one side of the plane is removed. The part left is called
a frustum of a cone
cone
cylinder
sphere
Step 1: Imagine a cone — it has a circular base and a pointed top (called the vertex).
Step 2: Now, take a plane (a flat surface) and cut the cone parallel to its base. "Parallel to the base" means the cutting plane is flat and at the same angle as the base, just at some height above it.
Step 3: After cutting, we remove the small cone (the top portion near the vertex).
Step 4: What remains is a shape with two circular surfaces: • one is the original big base (at the bottom), • the other is the new smaller circular face (at the top, where we cut). The sides are still slanting.
Step 5: This new solid (with two parallel circular ends and slanting sides) is called a frustum of a cone.
Therefore, the correct answer is: A frustum of a cone.