A4. Below you see a construction sheet with which you can fold a so-called dipiramide. This dipiramide is shown in the picture on the right.

Which three points from the construction sheet become vertices of the gray triangle after folding?
A) $F, G$ and $L$
B) $H, I$ and $M$
C) $G, H$ and $I$
D) $H, K$ and $L$
E) $F, I$ and $K$
![](https://cdn.mathpix.com/cropped/2024_04_17_dd45dfb811a24abc1595g-1.jpg?height=384&width=1128&top_left_y=2286&top_left_x=477)
A4. B) $H, I$ and $M$ Different letters can belong to the same vertex of the dipiramide. The five vertices are: $G=F=J, K=M, H, I$ and $L$. Points $H$ and $I$ have four neighbors, so they are vertices of the gray triangle. Point $K=M$ also has four neighbors: $I, H, L$ and $G=F=J$, so that is the last vertex of the gray triangle.