A pure resistor consumes only real power ($P = VI$).

The power factor of a pure resistive circuit is unity ($\cos 0° = 1$).

Voltage and current reach their maximum, minimum, and zero values at the same instant in time.

Zero phase distortion

Power factor is always unity

Dissipates electrical energy as heat ($I^2R$ loss)

Cannot store energy like an inductor or capacitor

Heating elements (heaters, irons)

Incandescent lighting

Calibration resistors in measuring instruments

In an inductive circuit, current lags voltage by $90°$.

In a capacitive circuit, current leads voltage by $90°$.

Option D ($90°$) is correct for a pure inductor or capacitor.