Trace the edges

On which of these shapes can you trace a path along all of its edges, without going over any edge twice?

Problem



Here are five poyhedra:

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Trace the Edges
Image
Trace the Edges
Image
Trace the Edges
Image
Trace the Edges
Image
Trace the Edges

You can trace a path along all of the edges, without going over any edge twice, on only one of these shapes.

Which shape is it and how do you do it?