The correct answer is Option (4) → (B), (C) and (D) only
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(A) Impedance is maximum (Incorrect): The impedance ($Z$) of a series RLC circuit is given by: $Z = \sqrt{R^2 + (X_L - X_C)^2}$
At resonance, since $X_L = X_C$, the term $(X_L - X_C)$ becomes zero. This results in the minimum possible impedance, which is simply equal to the resistance ($R$). Consequently, the current in the circuit is at its maximum.
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(B) $X_C = X_L$ (Correct): This is the fundamental condition for resonance. The two reactances oppose each other perfectly.
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(C) $Z = R$ (Correct): As shown in the formula above, when $X_L = X_C$, the impedance $Z$ simplifies to $\sqrt{R^2}$, which is $R$. The circuit behaves as a purely resistive circuit.
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(D) $\omega = \frac{1}{\sqrt{LC}}$ (Correct): Resonance occurs at angular frequency: $\omega = \frac{1}{\sqrt{LC}}$m.
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