What is the primary reason voltage can be greater across reactances in series than the applied voltage?

The primary reason voltage can be greater across reactances in series than the applied voltage is resonance. When a circuit is in resonance, the inductive and capacitive reactances cancel each other out at a specific frequency, leading to a condition where the overall impedance of the circuit is minimized.

At this resonant frequency, the voltage across each reactance can significantly exceed the supply voltage due to the energy being exchanged between the inductor and capacitor. This results in a situation where the reactive components amplify the voltage across themselves, thus appearing greater than the total voltage applied to the series circuit. This phenomenon is commonly observed in RLC circuits, where the combined effect of inductance and capacitance at resonance creates high peaks of voltage across those components.

The other options, while related to electrical properties, do not primarily lead to a situation where the voltage across reactances exceeds the applied voltage.