Octahedron :
Euler's formula : $$V + F - E = 2$$ where V is number of vertices , F is number of faces and E is number of edges.
Octahedron has 6 vertices and 8 faces.
=> $$E = V + F - 2 = 6 + 8 - 2$$
=> $$E = 14 - 2 = 12$$
=> Ans - (B)
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