According to Rankine's theory, the failure occurs at a point in a member

• A. when the maximum shear stress in a bi-axial stress system reaches the shear stress at elastic limit in a simple tension test
• B. when the maximum principal stress in a bi-axial stress system reaches the elastic limit of the material in a simple tension test
• C. when the strain energy per unit volume in a bi-axial stress system reaches the strain energy at the elastic limit per unit volume as determined from a simple tension test
• D. when the maximum principal strain in a bi-axial stress system reaches the strain at the elastic limit as determined from a simple tension test