According to maximum normal stress theory, the maximum normal stress in the shaft is
A
$$\frac{1}{2}\sqrt {{\sigma ^2} \times 4{\tau ^2}} $$
B
$$\sqrt {{\sigma ^2} \times 4{\tau ^2}} $$
C
$$\frac{1}{2}\left( {\sigma + \sqrt {{\sigma ^2} \times 4{\tau ^2}} } \right)$$
D
$$\sigma + \sqrt {{\sigma ^2} \times 4{\tau ^2}} $$
Correct Answer: $$\frac{1}{2}\left( {\sigma + \sqrt {{\sigma ^2} \times 4{\tau ^2}} } \right)$$