Which of the following materials must be maintained to avoid structural hazards?

Wood is a material known for its susceptibility to a variety of conditions that can lead to deterioration and structural hazards if not properly maintained. Over time, wood can be affected by moisture, pests, and fungal growth, all of which can compromise its structural integrity. Regular inspections and maintenance are essential to ensure that any signs of rot, insect infestation, or moisture damage are promptly addressed, thereby preventing potential failures in structural support.

In contrast, while plastic, glass, and concrete are also important materials that have their own maintenance requirements, they do not present the same level of structural vulnerability as untreated wood. Plastic can degrade from UV exposure, glass can break, and concrete can crack, but these issues may not necessarily lead directly to a structural hazard in the same way that failing wooden components can. Hence, the emphasis on wood maintenance is critical for ensuring safety and structural soundness in building applications.