Find the odd one from the following:

Let's analyze the placement of the small black triangle inside the outer boundary square across the options:
* In Option B, the triangle is positioned exactly at a vertex/corner (Top-Right).
* In Option C, the triangle is positioned exactly at a vertex/corner (Top-Left).
* In Option D, the triangle is positioned exactly at a vertex/corner (Bottom-Right).
* In Option A, the triangle is positioned along the flat straight edge (Bottom-center), not at any corner vertex.

Since Option A has a completely different structural placement logic compared to the other three corner-bound options, it is the odd one out.