Final answer:
A masonry wall relies on vertical compression forces for its strength. Without the load from a roof, which acts as compressive stress, the wall is compromised and at risk of collapse from lateral impacts.
Step-by-step explanation:
A masonry wall relies on vertical compression forces to keep it strong. If the wood roof on a masonry wall burns down, the wall is no longer sound because it lost the load that was strengthening it. Any lateral impact load on the wall can cause collapse. The correct answer to the question is c) Vertical compression forces.
From an engineering standpoint, the weight of a roof acts as a compressive load on the walls, which helps the walls to remain stable. Without this load, the walls lose an important component of their structural stability. Additionally, structures like bones are more likely to fracture due to shear stress rather than tension or compression, similar to how lateral impacts can affect masonry walls.