Shear stress distribution on the cross-section of the coil wire in a helical compression spring is shown in the figure. This shear stress distribution represents

• A. torsional shear stress in the coil wire cross-section
• B. combined direct shear and torsional shear stress in the coil wire cross-section
• C. direct shear stress in the coil wire cross-section
• D. combined direct shear and torsional shear stress along with the effect of stress concentration at inside edge of the coil wire cross-section