Shape A, B and C all have 4 sides and 4 corners, but can you see that Shape D has 5 sides and 5 corners. This is the odd one out. A shape with 5 sides and 5 corners is called a pentagon.

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The rectangle is a wobbly, unstable shape. When you push the side, it flops into a slanted parallelogram. This happens without any of the rectangle's sides changing length.

This polytope is actually a truncated octahedron, a shape with 14 sides (six squares and eight regular hexagons). And truncated octahedra can create a space-filling tiling of 3-space.