Which type of line exhibits no standing waves of current and voltage?

The type of line that exhibits no standing waves of current and voltage is the matched line. In transmission lines, standing waves are created when there is a mismatch between the load impedance and the characteristic impedance of the line. This mismatch causes reflections of the signal, resulting in standing waves of voltage and current along the line.

A matched line means that the load impedance is perfectly matched to the characteristic impedance of the line. This alignment allows for maximum power transfer and eliminates reflections, thus preventing the formation of standing waves. As a result, the current and voltage remain constant along the length of the line, providing a stable operation without unwanted variations.

In contrast, other options like nonsinusoidal, nonresonant, and harmonic might imply different characteristics of signals or waves but do not specifically address the concept of impedance matching and its direct effect on standing waves. Therefore, the matched line stands out as the definitive choice in preventing standing waves of current and voltage.