Which of the following dice is not a platonic solid?

The story behind the answer

10-sided die is correct because it isn’t a Platonic solid. Standard d10s are pentagonal trapezohedra: their 10 faces are congruent kites (not regular polygons), and the vertices aren’t all equivalent. In contrast, the 8-, 12-, and 20-sided dice correspond to true Platonic solids: octahedron (8), dodecahedron (12), and icosahedron (20), each with identical regular faces and identical vertices.

Context tip: There are only five Platonic solids—tetrahedron (4