3. Bow, crook, cup and twist are all __ . b. Types of screws c. Methods of sawing d. Types of lumber defects

The correct answer is b. Types of screws.<br /><br />Bow, crook, cup, and twist are all types of defects that can occur in lumber, but they are not methods of sawing. They are not types of screws either. These terms refer to the curvature or deformation that can occur in the wood, such as a bow being a curve along the length of the board, a crook being a curve along the width, a cup being a curve along the thickness, and a twist being a combination of bow and crook along the length and width.