Step 1: Average Power Formula.
The average power dissipated in an AC circuit is given by:
\[
P_{\text{avg}} = V_{\text{rms}} I_{\text{rms}} \cos(\phi)
\]
where \( \phi \) is the phase difference between the voltage and current. Since both voltage and current have the same phase, \( \cos(\phi) = 1 \). Thus, the average power is:
\[
P = 250 \, \text{W}.
\]
Step 2: Conclusion.
The correct answer is (B), 250 W.