The voltage of an ac source varies with time according to the equation `V = 100 sin 100 pit cos 100 pit` where t is in seconds and V is in volt. Then
A. The peak voltage of the source is 100 volts
B. The peak voltage of the source is 50 volt
C. The peak voltage of the source is `100//sqrt(2)` volts
D. The frequency of the source is 50 Hz