rectangular prisms (including cubes). maybe some other ones I'm not thinking of now too.
A cube has six flat surfaces, but so do other solids. Look up 'hexahedron' in wikipedia.
Spheres
Circles, squares, rectangles, and triangles are solids that have a flat surface.
2
Cube, rectangular prism
A cylinder
A cuboid has got six flat surfaces.
A cube has 6 flat surfaces. Most boxes of all shapes also have six flat surfaces
Six faces are flat.
true
A cube
None. A cuboid has six flat surfaces.