The correct answer is C) reduced at the bow and stern. In ship construction, the frame spacing is reduced at the bow and stern to accommodate the increased stresses and curvature in these areas. The bow and stern experience greater bending and shear forces, so the frame spacing is decreased to provide additional structural support and rigidity in these critical regions of the vessel. The other options are incorrect because: B) uniform frame spacing over the length of the vessel is not accurate, and D) while frame spacing may be reduced in machinery spaces, this is not the primary reason for the reduced spacing at the bow and stern.