When a shaft is subjected to combined twisting moment (T) and bending moment (M), then the equivalent twisting moment is equal to

A. $$\frac{1}{2}\sqrt {{{\text{M}}^2} + {{\text{T}}^2}} $$

B. $$\sqrt {{{\text{M}}^2} + {{\text{T}}^2}} $$

C. $$\frac{1}{2}\left( {{\text{M}} + \sqrt {{{\text{M}}^2} + {{\text{T}}^2}} } \right)$$

D. $${\text{M}} + \sqrt {{{\text{M}}^2} + {{\text{T}}^2}} $$

Answer: Option B