In an RCL circuit a second capacitor is added in parallel to the capacitor already present. Does the resonant frequency of the circuit increase, decrease, or remain the same? 

(a) The resonant frequency increases, because it depends inversely on the square root of the capacitance, and the equivalent capacitance decreases when a second capacitor is added in parallel. 

(b) The resonant frequency increases, because it is directly proportional to the capacitance, and the equivalent capacitance increases when a second capacitor is added in parallel. 

(c) The resonant frequency decreases, because it is directly proportional to the capacitance, and the equivalent capacitance decreases when a second capacitor is added in parallel. 

(d) The resonant frequency decreases, because it depends inversely on the square root of the capacitance, and the equivalent capacitance increases when a second capacitor is added in parallel. 

(e) The resonant frequency remains the same.