Which of the geometrical figures has infinite lines of symmetry?
Circle
A circle has infinite number of lines of symmetry. All the secants passing through the center are the lines of symmetry.
A regular decagon has 10 lines of symmetry because it has 10 equal sides.
In the case of prism symmetry depends upon the shape of a triangle that we are taking e.g. for an isosceles triangular-based prism has 2 planes of symmetry. An equilateral triangular-based prism has four planes of symmetry. An equilateral triangular-based triangular-based prism has four planes of symmetry. An equilateral triangular based prism has four planes of symmetry.
A pyramid being three-dimensional does not have lines of symmetry.
Hence the correct option is A