____ represents the "was-wood" material with the least engineering and thus the most natural fiber bonding.

The term that best describes the "was-wood" material with the least engineering and the most natural fiber bonding is plywood. Plywood is manufactured from thin layers of wood veneer that are glued together, with the grain of each layer arranged perpendicularly to the adjacent one. This cross-lamination process provides strength and stability while still allowing the natural characteristics of the wood fibers to influence the final product.

The minimal engineering involved in plywood relative to other options means it retains more of the natural wood properties. The layers are bonded using adhesives that do not significantly alter the wood's inherent fibers, which is a key point of distinction when compared to engineered materials like particle board and fiberboard. These engineered products typically involve the use of artificial fibers, binders, and other materials, which diminish the natural bonding and structural qualities of the wood.

Thus, plywood exemplifies a material that is closer to its natural state while still being viable for construction and other applications, making it the correct answer.