Step 1: Concept
Magnetic moment ($M$) of a revolving electron is $M = I \times A$.
Step 2: Current and Area
Current $I = \frac{e}{T} = \frac{e}{(2\pi r / v)} = \frac{ev}{2\pi r}$
Area $A = \pi r^2$
Step 3: Calculation
$M = \left( \frac{ev}{2\pi r} \right) \times (\pi r^2)$
$M = \frac{evr}{2}$
Step 4: Conclusion
The magnetic moment is $\frac{evr}{2}$.
Final Answer:(B)