STEP - BY - STEP EXPLANATION
What to find?
The platonic solid that has twenty faces that are equilateral triangles.
Given:
Platonic solid.
Let's check each option.
A hexahedron is a polyhedron with 6 faces.
So this is not an option.
An octahedron is a polyhedron with 8 faces.
This option is also ruled out.
A Dodecahedron is a polyhedron with 12 faces.
This is also not an option.
An Icosahedron is a polyhedron whose faces are 20 equilateral triangles.
Hence Icosahedron is the correct option.
ANSWER
C. Icosahedron