In a right circular cone , the cross-section made by a plane parallel to the base is a
(a) circle (b) frustyum of a cone (c) sphere (d) hemisphere
When a plane parallel to the base of a cone cuts it, then a frustum and a smaller cone is formed.
The cross-section thus formed will be a circle.
Hence, the correct answer is option (a).
RD Sharma (2016)