At series resonance, the phase angle between applied voltage and circuit is ___________

The correct answer is C. 0°.

At series resonance, the inductive reactance and capacitive reactance cancel each other out, leaving only the resistance in the circuit. This means that the current and voltage are in phase with each other, and the phase angle is 0°.

Option A is incorrect because the phase angle is 0° at resonance, not 90°.

Option B is incorrect because the phase angle is 0° at resonance, not 180°.

Option D is incorrect because there is a correct answer.