If σ1 and σ2 be the major and minor tensile stresses, then maximum value of tangential stress is equal to

• A. σ2
• B. σ1 - σ2
• C. σ1 + σ2
• D. \(\frac{{{{\rm{\sigma }}_1}{\rm{\;}} - {\rm{\;}}{{\rm{\sigma }}_2}}}{2}\)