The correct decomposition of the polygon (square) into \( n-2 \) triangles, where \( n \) is the number of vertices of the polygon, is as follows:
A square has 4 vertices (A, B, C, D), so \( n-2 = 4-2 = 2 \). Therefore, the polygon should be decomposed into 2 triangles.
- Figure 1 can be seen to decompose the square into 2 triangles by connecting both diagonals, resulting in 4 triangles total, but only 2 distinct triangles from the perspective of decomposing it down.
- Figure 2, however, directly connects the vertices B and D, indicating that it clearly provides a valid decomposition into 2 triangles.
Thus, the correct response is:
Figure 2 is the correct decomposition because it has n−2=4−2=2 triangles.