In a right circular cone, the cross-section made by a plane parallel to the base is a
circle
frustum of a cone
sphere
hemisphere
Step 1: A right circular cone has a circular base and a pointed top (vertex).
Step 2: The base of the cone is a circle. Now imagine a flat surface (a plane) cutting the cone, but this plane is kept parallel to the base.
Step 3: When the cutting plane is parallel to the base, the shape of the cut (cross-section) will be the same shape as the base.
Step 4: Since the base is a circle, the cross-section is also a circle.
Final Answer: The cross-section is a circle (Option A).