The voltage of an ac supply varies with time (t) I as\[V=120\,\sin \,100\pi \,t\,\cos \,100\pi t\]. The maximum voltage and frequency respectively are

• A. 120 volts, 100 Hz
• B. \[\frac{120}{\sqrt{2}}volts,\,\,100Hz\]
• C. 60 volts, 200 Hz 
• D. 60 volts, 100 Hz