Checks are defined as separations of wood fibers, through growth rings, parallel to the grain.

• A. Separations of the wood fibers, between growth rings, parallel to grain
• B. Separations of the wood fibers, through growth rings, parallel to grain
• C. Advanced checks that extend completely through the wood
• D. Groups of cells running from the center to the bark

Answer: (B)

Checks form as cracks that develop in wood when it dries and shrinks unevenly, so the break propagates along the grain and cuts through the successive growth rings. This orientation—parallel to the grain and crossing the growth rings—describes a separation of wood fibers that extends along the length of the piece while passing across ring boundaries. That’s why this description fits best. The other ideas describe different features: cracks that occur between rings, larger through-cracks, or cellular structures that run from center to edge, none of which capture the specific, grain-parallel crack crossing growth rings.