In an A.C. circuit the emf (e) and the current (i) at any instant are given respectively by : <br> $e=E_0 \sin \omega t$ <br> $i=I_0 \sin(\omega t-\phi)$ <br>The average power in the circuit over one cycle of A.C. is -

Question

( A ) $E_0 I_0$
( B ) $\frac{E_0 I_0}{2} \sin \phi$
( C ) $\frac{E_0 I_0}{2}$
( D ) $\frac{E_0 I_0}{2} \cos \phi $