What is plywood commonly made of?

Plywood is constructed by layering thin sheets of wood veneer, known as plies or veneers, where three or more layers are bonded together with adhesives under heat and pressure. This cross-laminated structure enhances its strength and stability, preventing warping and cracking that can occur in a single piece of wood. The orientation of the grains in each layer is typically arranged at right angles to one another, adding to the strength and durability of the plywood. This makes it an ideal choice for various construction and roofing applications, as it offers both resilience and flexibility.

The other options do not accurately represent the composition of plywood, as they involve materials or construction methods that are not related to wood veneer sheets.