If fbt and fc are the co-existent bending tensile stress and shear stress in a member, the equivalent stress fc is

• A. <img src="/_files/images/civil-engineering/steel-structure-design/107-14-189-1.png">
• B. <img src="/_files/images/civil-engineering/steel-structure-design/107-14-189-2.png">
• C. <img src="/_files/images/civil-engineering/steel-structure-design/107-14-189-3.png">
• D. <img src="/_files/images/civil-engineering/steel-structure-design/107-14-189-4.png">