The correct answer is option 'D', the waveform of the load current will be triangular when a single-phase voltage source square-wave inverter feeds a pure inductive load.

Explanation:

When a single-phase voltage source square-wave inverter is used, the output voltage waveform is a square wave. This means that the voltage across the load will switch between two values - the positive peak voltage and the negative peak voltage.

When the load connected to the inverter is purely inductive, the current through an inductor lags the voltage across it by 90 degrees. This is due to the inherent nature of inductors to oppose changes in current.

Now, let's analyze the waveform of the load current when a square wave voltage is applied to an inductive load:

1. Positive Half-Cycle:
During the positive half-cycle of the square wave voltage, the voltage across the load becomes positive. Initially, the current is zero because the inductor opposes any change in current. As the positive voltage is applied, the current starts to increase linearly with time. The rate of increase of current is determined by the inductance value and the applied voltage. Thus, the current rises in a linear ramp-like manner.

2. Zero Crossing:
At the zero crossing of the square wave voltage, the voltage across the load becomes zero. However, the current through the inductor cannot change instantaneously, so it continues to flow in the same direction.

3. Negative Half-Cycle:
During the negative half-cycle of the square wave voltage, the voltage across the load becomes negative. The inductor now opposes the decrease in current, causing the current to decrease linearly with time. The rate of decrease of current is determined by the inductance value and the applied voltage. Thus, the current decreases in a linear ramp-like manner.

This linear ramp-like waveform of the load current during each half-cycle forms a triangular waveform. Hence, the waveform of the load current when a single-phase voltage source square-wave inverter feeds a pure inductive load is triangular.