The mean and rms value of an alternating voltage for half cycle as shown in figure are respectively : 

• A

  ${\mathrm{V}}_0, {\mathrm{V}}_0$

• B

  $\frac{{\mathrm{V}}_0}{2}, {\mathrm{V}}_0$

• C

  $\frac{3{\mathrm{V}}_0}{2}, \frac{{\mathrm{V}}_0}{2}$

• D

  $\frac{{\mathrm{V}}_0}{4}, \frac{{\mathrm{V}}_0}{2}$