The power factor at resonance in R-L-C parallel circuit is

Zero
0.08 lagging
0.8 leading
Unity

The correct answer is D. Unity.

At 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, and the power factor is unity.

Option A is incorrect because the power factor is never zero in a parallel circuit.

Option B is incorrect because the power factor is never 0.08 lagging in a parallel circuit.

Option C is incorrect because the power factor is never 0.8 leading in a parallel circuit.