If in a series L-C-R AC circuit, the voltages across L, C and R are V1, V2 and V3 respectively, then the voltage of the source is always:

Explanation

In a series L-C-R AC circuit, the voltages across the inductor (L), capacitor (C), and resistor (R) have phase differences due to their reactive nature. The voltage across the inductor leads the current by 90 degrees, the voltage across the capacitor lags the current by 90 degrees, and the voltage across the resistor is in phase with the current. Therefore, the source voltage is not just the arithmetic sum of V1, V2, and V3 because of the phase differences. Instead, it is calculated using vector addition (phasor sum). The correct option is 'none of these' because the simple addition or subtraction of voltages without accounting for phase is incorrect. The incorrect options fail to consider these phase differences.