The correct answer is A. Non-sinusoidal.
Corona discharge is a form of electrical discharge that occurs in the air when a high voltage is applied to a conductor. It is characterized by a bluish glow that can be seen around the conductor. Corona discharge can cause power losses and can also damage insulators.
The current drawn by the line due to corona losses is non-sinusoidal because the discharge is not a continuous process. It occurs in a series of pulses, and the current waveform is therefore a series of spikes.
The other options are incorrect because they describe waveforms that are continuous. A sinusoidal waveform is a smooth, wave-like curve that repeats itself over and over again. A triangular waveform is a three-sided shape that starts at zero, goes up to a maximum value, and then goes back down to zero. A square waveform is a four-sided shape that starts at zero, goes up to a maximum value, stays at that value for a period of time, and then goes back down to zero.