Final answer:
An octahedron is the figure with 6 plane faces, despite the mentioned sources inaccurately describing it. It is a polyhedron with eight faces and six vertices. None of the other options match the description given as hexagons, dodecahedrons, and icosahedrons do not have six faces.
Step-by-step explanation:
The question asks to identify a figure with 6 plane faces. The options given are a hexagon, octahedron, dodecahedron, and icosahedron. Out of the options provided, an octahedron is the correct answer because it is a polyhedron with eight faces. However, according to provided information, an octahedron is stated mistakenly as having six corners and eight sides, which suggests a possible typographical error in your sources. The correct definition of an octahedron should mention that it has eight faces, not sides, which meet at six vertices. None of the other figures listed match the description. A hexagon has only six sides and is a two-dimensional shape, a dodecahedron has twelve faces, and an icosahedron is described as having 20 faces. Therefore, the octahedron is the best answer provided we correct the typographical error regarding the number of faces.