4. A 12 ohm resistor, a 40 F capacitor, and an 8 mH coil are in series across an ac source. The resonant frequency is
A. 281 Hz
B. 28.1 Hz
C. 10 kHz
D. 2,810 Hz
4. A 12 ohm resistor, a 40 F capacitor, and an 8 mH coil are in series across an ac source. The resonant frequency is
A. 281 Hz
B. 28.1 Hz
C. 10 kHz
D. 2,810 Hz