A tetrahedron is a solid figure with 6 edges.
There's no such thing as solid edges.
A tetrahedron is a triangular pyramid, with 4 vertices, 6 edges and 4 triangular faces. In a regular tetrahedron (the first Platonic solid) all triangles are equilateral.
6
It is a hexahedron
You have to count the lines on a solid figure
There is no solid figure with only four edges. The smallest solid figure is the tetrahedron, made up of four triangular faces, but it has six edges.
A triangular prism
cube
A triangular pyramid has 4 faces and has 6 edges
A basic pyramid with three sides?
A triangular pyramid.
A tetrahedron.
square
No normal polyhedron.